diff --git a/stl/src/filesystem.cpp b/stl/src/filesystem.cpp
index a8493ec49ae..15d42a2ed7d 100644
--- a/stl/src/filesystem.cpp
+++ b/stl/src/filesystem.cpp
@@ -253,8 +253,7 @@ void __stdcall __std_fs_directory_iterator_close(_In_ const __std_fs_dir_handle
 
     if (_Code_page == __std_code_page{CP_UTF8} || _Code_page == __std_code_page{54936}) {
         // For UTF-8 or GB18030, attempt to use WC_ERR_INVALID_CHARS. (These codepages can't use WC_NO_BEST_FIT_CHARS
-        // below, and other codepages can't use WC_ERR_INVALID_CHARS.) WC_ERR_INVALID_CHARS is Windows Vista+.
-        // Windows XP will activate the ERROR_INVALID_FLAGS fallback below.
+        // below, and other codepages can't use WC_ERR_INVALID_CHARS.)
         _Result._Len = WideCharToMultiByte(static_cast<unsigned int>(_Code_page), WC_ERR_INVALID_CHARS, _Input_str,
             _Input_len, _Output_str, _Output_len, nullptr, nullptr);
     } else { // For other codepages, attempt to use WC_NO_BEST_FIT_CHARS.
diff --git a/stl/src/winapinls.cpp b/stl/src/winapinls.cpp
index 44f792e55a4..38e2b0c63f8 100644
--- a/stl/src/winapinls.cpp
+++ b/stl/src/winapinls.cpp
@@ -1,625 +1,11 @@
 // Copyright (c) Microsoft Corporation.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-#include "awint.hpp"
-
-#if _STL_WIN32_WINNT < _WIN32_WINNT_VISTA
-
-#include <algorithm>
-#include <cctype>
-#include <cstdlib> // for _countof
-#include <string_view>
-
-namespace {
-    struct LCIDTOLOCALENAME {
-        LCID lcid;
-        const wchar_t* localeName;
-    };
-
-    struct LOCALENAMEINDEX {
-        const wchar_t* name;
-        int index;
-    };
-
-    // Map of LCID to locale name for Windows XP.
-    // Data in this table has been obtained from National Language Support (NLS) API Reference.
-    // The table is sorted to improve search performance.
-    // clang-format off
-    constexpr LCIDTOLOCALENAME LcidToLocaleNameTable[] = {
-        { 0x0001, L"ar"         },
-        { 0x0002, L"bg"         },
-        { 0x0003, L"ca"         },
-        { 0x0004, L"zh-CHS"     },
-        { 0x0005, L"cs"         },
-        { 0x0006, L"da"         },
-        { 0x0007, L"de"         },
-        { 0x0008, L"el"         },
-        { 0x0009, L"en"         },
-        { 0x000A, L"es"         },
-        { 0x000B, L"fi"         },
-        { 0x000C, L"fr"         },
-        { 0x000D, L"he"         },
-        { 0x000E, L"hu"         },
-        { 0x000F, L"is"         },
-        { 0x0010, L"it"         },
-        { 0x0011, L"ja"         },
-        { 0x0012, L"ko"         },
-        { 0x0013, L"nl"         },
-        { 0x0014, L"no"         },
-        { 0x0015, L"pl"         },
-        { 0x0016, L"pt"         },
-        { 0x0018, L"ro"         },
-        { 0x0019, L"ru"         },
-        { 0x001A, L"hr"         },
-        { 0x001B, L"sk"         },
-        { 0x001C, L"sq"         },
-        { 0x001D, L"sv"         },
-        { 0x001E, L"th"         },
-        { 0x001F, L"tr"         },
-        { 0x0020, L"ur"         },
-        { 0x0021, L"id"         },
-        { 0x0022, L"uk"         },
-        { 0x0023, L"be"         },
-        { 0x0024, L"sl"         },
-        { 0x0025, L"et"         },
-        { 0x0026, L"lv"         },
-        { 0x0027, L"lt"         },
-        { 0x0029, L"fa"         },
-        { 0x002A, L"vi"         },
-        { 0x002B, L"hy"         },
-        { 0x002C, L"az"         },
-        { 0x002D, L"eu"         },
-        { 0x002F, L"mk"         },
-        { 0x0036, L"af"         },
-        { 0x0037, L"ka"         },
-        { 0x0038, L"fo"         },
-        { 0x0039, L"hi"         },
-        { 0x003E, L"ms"         },
-        { 0x003F, L"kk"         },
-        { 0x0040, L"ky"         },
-        { 0x0041, L"sw"         },
-        { 0x0043, L"uz"         },
-        { 0x0044, L"tt"         },
-        { 0x0046, L"pa"         },
-        { 0x0047, L"gu"         },
-        { 0x0049, L"ta"         },
-        { 0x004A, L"te"         },
-        { 0x004B, L"kn"         },
-        { 0x004E, L"mr"         },
-        { 0x004F, L"sa"         },
-        { 0x0050, L"mn"         },
-        { 0x0056, L"gl"         },
-        { 0x0057, L"kok"        },
-        { 0x005A, L"syr"        },
-        { 0x0065, L"div"        },
-        { 0x007f, L""           },
-        { 0x0401, L"ar-SA"      },
-        { 0x0402, L"bg-BG"      },
-        { 0x0403, L"ca-ES"      },
-        { 0x0404, L"zh-TW"      },
-        { 0x0405, L"cs-CZ"      },
-        { 0x0406, L"da-DK"      },
-        { 0x0407, L"de-DE"      },
-        { 0x0408, L"el-GR"      },
-        { 0x0409, L"en-US"      },
-        { 0x040B, L"fi-FI"      },
-        { 0x040C, L"fr-FR"      },
-        { 0x040D, L"he-IL"      },
-        { 0x040E, L"hu-HU"      },
-        { 0x040F, L"is-IS"      },
-        { 0x0410, L"it-IT"      },
-        { 0x0411, L"ja-JP"      },
-        { 0x0412, L"ko-KR"      },
-        { 0x0413, L"nl-NL"      },
-        { 0x0414, L"nb-NO"      },
-        { 0x0415, L"pl-PL"      },
-        { 0x0416, L"pt-BR"      },
-        { 0x0418, L"ro-RO"      },
-        { 0x0419, L"ru-RU"      },
-        { 0x041A, L"hr-HR"      },
-        { 0x041B, L"sk-SK"      },
-        { 0x041C, L"sq-AL"      },
-        { 0x041D, L"sv-SE"      },
-        { 0x041E, L"th-TH"      },
-        { 0x041F, L"tr-TR"      },
-        { 0x0420, L"ur-PK"      },
-        { 0x0421, L"id-ID"      },
-        { 0x0422, L"uk-UA"      },
-        { 0x0423, L"be-BY"      },
-        { 0x0424, L"sl-SI"      },
-        { 0x0425, L"et-EE"      },
-        { 0x0426, L"lv-LV"      },
-        { 0x0427, L"lt-LT"      },
-        { 0x0429, L"fa-IR"      },
-        { 0x042A, L"vi-VN"      },
-        { 0x042B, L"hy-AM"      },
-        { 0x042C, L"az-AZ-Latn" },
-        { 0x042D, L"eu-ES"      },
-        { 0x042F, L"mk-MK"      },
-        { 0x0432, L"tn-ZA"      },
-        { 0x0434, L"xh-ZA"      },
-        { 0x0435, L"zu-ZA"      },
-        { 0x0436, L"af-ZA"      },
-        { 0x0437, L"ka-GE"      },
-        { 0x0438, L"fo-FO"      },
-        { 0x0439, L"hi-IN"      },
-        { 0x043A, L"mt-MT"      },
-        { 0x043B, L"se-NO"      },
-        { 0x043E, L"ms-MY"      },
-        { 0x043F, L"kk-KZ"      },
-        { 0x0440, L"ky-KG"      },
-        { 0x0441, L"sw-KE"      },
-        { 0x0443, L"uz-UZ-Latn" },
-        { 0x0444, L"tt-RU"      },
-        { 0x0445, L"bn-IN"      },
-        { 0x0446, L"pa-IN"      },
-        { 0x0447, L"gu-IN"      },
-        { 0x0449, L"ta-IN"      },
-        { 0x044A, L"te-IN"      },
-        { 0x044B, L"kn-IN"      },
-        { 0x044C, L"ml-IN"      },
-        { 0x044E, L"mr-IN"      },
-        { 0x044F, L"sa-IN"      },
-        { 0x0450, L"mn-MN"      },
-        { 0x0452, L"cy-GB"      },
-        { 0x0456, L"gl-ES"      },
-        { 0x0457, L"kok-IN"     },
-        { 0x045A, L"syr-SY"     },
-        { 0x0465, L"div-MV"     },
-        { 0x046B, L"quz-BO"     },
-        { 0x046C, L"ns-ZA"      },
-        { 0x0481, L"mi-NZ"      },
-        { 0x0801, L"ar-IQ"      },
-        { 0x0804, L"zh-CN"      },
-        { 0x0807, L"de-CH"      },
-        { 0x0809, L"en-GB"      },
-        { 0x080A, L"es-MX"      },
-        { 0x080C, L"fr-BE"      },
-        { 0x0810, L"it-CH"      },
-        { 0x0813, L"nl-BE"      },
-        { 0x0814, L"nn-NO"      },
-        { 0x0816, L"pt-PT"      },
-        { 0x081A, L"sr-SP-Latn" },
-        { 0x081D, L"sv-FI"      },
-        { 0x082C, L"az-AZ-Cyrl" },
-        { 0x083B, L"se-SE"      },
-        { 0x083E, L"ms-BN"      },
-        { 0x0843, L"uz-UZ-Cyrl" },
-        { 0x086B, L"quz-EC"     },
-        { 0x0C01, L"ar-EG"      },
-        { 0x0C04, L"zh-HK"      },
-        { 0x0C07, L"de-AT"      },
-        { 0x0C09, L"en-AU"      },
-        { 0x0C0A, L"es-ES"      },
-        { 0x0C0C, L"fr-CA"      },
-        { 0x0C1A, L"sr-SP-Cyrl" },
-        { 0x0C3B, L"se-FI"      },
-        { 0x0C6B, L"quz-PE"     },
-        { 0x1001, L"ar-LY"      },
-        { 0x1004, L"zh-SG"      },
-        { 0x1007, L"de-LU"      },
-        { 0x1009, L"en-CA"      },
-        { 0x100A, L"es-GT"      },
-        { 0x100C, L"fr-CH"      },
-        { 0x101A, L"hr-BA"      },
-        { 0x103B, L"smj-NO"     },
-        { 0x1401, L"ar-DZ"      },
-        { 0x1404, L"zh-MO"      },
-        { 0x1407, L"de-LI"      },
-        { 0x1409, L"en-NZ"      },
-        { 0x140A, L"es-CR"      },
-        { 0x140C, L"fr-LU"      },
-        { 0x141A, L"bs-BA-Latn" },
-        { 0x143B, L"smj-SE"     },
-        { 0x1801, L"ar-MA"      },
-        { 0x1809, L"en-IE"      },
-        { 0x180A, L"es-PA"      },
-        { 0x180C, L"fr-MC"      },
-        { 0x181A, L"sr-BA-Latn" },
-        { 0x183B, L"sma-NO"     },
-        { 0x1C01, L"ar-TN"      },
-        { 0x1C09, L"en-ZA"      },
-        { 0x1C0A, L"es-DO"      },
-        { 0x1C1A, L"sr-BA-Cyrl" },
-        { 0x1C3B, L"sma-SE"     },
-        { 0x2001, L"ar-OM"      },
-        { 0x2009, L"en-JM"      },
-        { 0x200A, L"es-VE"      },
-        { 0x203B, L"sms-FI"     },
-        { 0x2401, L"ar-YE"      },
-        { 0x2409, L"en-CB"      },
-        { 0x240A, L"es-CO"      },
-        { 0x243B, L"smn-FI"     },
-        { 0x2801, L"ar-SY"      },
-        { 0x2809, L"en-BZ"      },
-        { 0x280A, L"es-PE"      },
-        { 0x2C01, L"ar-JO"      },
-        { 0x2C09, L"en-TT"      },
-        { 0x2C0A, L"es-AR"      },
-        { 0x3001, L"ar-LB"      },
-        { 0x3009, L"en-ZW"      },
-        { 0x300A, L"es-EC"      },
-        { 0x3401, L"ar-KW"      },
-        { 0x3409, L"en-PH"      },
-        { 0x340A, L"es-CL"      },
-        { 0x3801, L"ar-AE"      },
-        { 0x380A, L"es-UY"      },
-        { 0x3C01, L"ar-BH"      },
-        { 0x3C0A, L"es-PY"      },
-        { 0x4001, L"ar-QA"      },
-        { 0x400A, L"es-BO"      },
-        { 0x440A, L"es-SV"      },
-        { 0x480A, L"es-HN"      },
-        { 0x4C0A, L"es-NI"      },
-        { 0x500A, L"es-PR"      },
-        { 0x7C04, L"zh-CHT"     },
-        { 0x7C1A, L"sr"         },
-    };
-    // clang-format on
-
-    static_assert(_STD is_sorted(_STD begin(LcidToLocaleNameTable), _STD end(LcidToLocaleNameTable),
-        [](const auto& left, const auto& right) { return left.lcid < right.lcid; }));
-
-    // Map of locale name to an index in LcidToLocaleNameTable, for Windows XP.
-    // Data in this table has been obtained from National Language Support (NLS) API Reference.
-    // The table is sorted to improve search performance.
-    // clang-format off
-    constexpr LOCALENAMEINDEX LocaleNameToIndexTable[] = {
-        { L""           , 66  },
-        { L"af"         , 44  },
-        { L"af-za"      , 113 },
-        { L"ar"         , 0   },
-        { L"ar-ae"      , 216 },
-        { L"ar-bh"      , 218 },
-        { L"ar-dz"      , 177 },
-        { L"ar-eg"      , 160 },
-        { L"ar-iq"      , 143 },
-        { L"ar-jo"      , 207 },
-        { L"ar-kw"      , 213 },
-        { L"ar-lb"      , 210 },
-        { L"ar-ly"      , 169 },
-        { L"ar-ma"      , 185 },
-        { L"ar-om"      , 196 },
-        { L"ar-qa"      , 220 },
-        { L"ar-sa"      , 67  },
-        { L"ar-sy"      , 204 },
-        { L"ar-tn"      , 191 },
-        { L"ar-ye"      , 200 },
-        { L"az"         , 41  },
-        { L"az-az-cyrl" , 155 },
-        { L"az-az-latn" , 107 },
-        { L"be"         , 33  },
-        { L"be-by"      , 99  },
-        { L"bg"         , 1   },
-        { L"bg-bg"      , 68  },
-        { L"bn-in"      , 125 },
-        { L"bs-ba-latn" , 183 },
-        { L"ca"         , 2   },
-        { L"ca-es"      , 69  },
-        { L"cs"         , 4   },
-        { L"cs-cz"      , 71  },
-        { L"cy-gb"      , 135 },
-        { L"da"         , 5   },
-        { L"da-dk"      , 72  },
-        { L"de"         , 6   },
-        { L"de-at"      , 162 },
-        { L"de-ch"      , 145 },
-        { L"de-de"      , 73  },
-        { L"de-li"      , 179 },
-        { L"de-lu"      , 171 },
-        { L"div"        , 65  },
-        { L"div-mv"     , 139 },
-        { L"el"         , 7   },
-        { L"el-gr"      , 74  },
-        { L"en"         , 8   },
-        { L"en-au"      , 163 },
-        { L"en-bz"      , 205 },
-        { L"en-ca"      , 172 },
-        { L"en-cb"      , 201 },
-        { L"en-gb"      , 146 },
-        { L"en-ie"      , 186 },
-        { L"en-jm"      , 197 },
-        { L"en-nz"      , 180 },
-        { L"en-ph"      , 214 },
-        { L"en-tt"      , 208 },
-        { L"en-us"      , 75  },
-        { L"en-za"      , 192 },
-        { L"en-zw"      , 211 },
-        { L"es"         , 9   },
-        { L"es-ar"      , 209 },
-        { L"es-bo"      , 221 },
-        { L"es-cl"      , 215 },
-        { L"es-co"      , 202 },
-        { L"es-cr"      , 181 },
-        { L"es-do"      , 193 },
-        { L"es-ec"      , 212 },
-        { L"es-es"      , 164 },
-        { L"es-gt"      , 173 },
-        { L"es-hn"      , 223 },
-        { L"es-mx"      , 147 },
-        { L"es-ni"      , 224 },
-        { L"es-pa"      , 187 },
-        { L"es-pe"      , 206 },
-        { L"es-pr"      , 225 },
-        { L"es-py"      , 219 },
-        { L"es-sv"      , 222 },
-        { L"es-uy"      , 217 },
-        { L"es-ve"      , 198 },
-        { L"et"         , 35  },
-        { L"et-ee"      , 101 },
-        { L"eu"         , 42  },
-        { L"eu-es"      , 108 },
-        { L"fa"         , 38  },
-        { L"fa-ir"      , 104 },
-        { L"fi"         , 10  },
-        { L"fi-fi"      , 76  },
-        { L"fo"         , 46  },
-        { L"fo-fo"      , 115 },
-        { L"fr"         , 11  },
-        { L"fr-be"      , 148 },
-        { L"fr-ca"      , 165 },
-        { L"fr-ch"      , 174 },
-        { L"fr-fr"      , 77  },
-        { L"fr-lu"      , 182 },
-        { L"fr-mc"      , 188 },
-        { L"gl"         , 62  },
-        { L"gl-es"      , 136 },
-        { L"gu"         , 55  },
-        { L"gu-in"      , 127 },
-        { L"he"         , 12  },
-        { L"he-il"      , 78  },
-        { L"hi"         , 47  },
-        { L"hi-in"      , 116 },
-        { L"hr"         , 24  },
-        { L"hr-ba"      , 175 },
-        { L"hr-hr"      , 90  },
-        { L"hu"         , 13  },
-        { L"hu-hu"      , 79  },
-        { L"hy"         , 40  },
-        { L"hy-am"      , 106 },
-        { L"id"         , 31  },
-        { L"id-id"      , 97  },
-        { L"is"         , 14  },
-        { L"is-is"      , 80  },
-        { L"it"         , 15  },
-        { L"it-ch"      , 149 },
-        { L"it-it"      , 81  },
-        { L"ja"         , 16  },
-        { L"ja-jp"      , 82  },
-        { L"ka"         , 45  },
-        { L"ka-ge"      , 114 },
-        { L"kk"         , 49  },
-        { L"kk-kz"      , 120 },
-        { L"kn"         , 58  },
-        { L"kn-in"      , 130 },
-        { L"ko"         , 17  },
-        { L"ko-kr"      , 83  },
-        { L"kok"        , 63  },
-        { L"kok-in"     , 137 },
-        { L"ky"         , 50  },
-        { L"ky-kg"      , 121 },
-        { L"lt"         , 37  },
-        { L"lt-lt"      , 103 },
-        { L"lv"         , 36  },
-        { L"lv-lv"      , 102 },
-        { L"mi-nz"      , 142 },
-        { L"mk"         , 43  },
-        { L"mk-mk"      , 109 },
-        { L"ml-in"      , 131 },
-        { L"mn"         , 61  },
-        { L"mn-mn"      , 134 },
-        { L"mr"         , 59  },
-        { L"mr-in"      , 132 },
-        { L"ms"         , 48  },
-        { L"ms-bn"      , 157 },
-        { L"ms-my"      , 119 },
-        { L"mt-mt"      , 117 },
-        { L"nb-no"      , 85  },
-        { L"nl"         , 18  },
-        { L"nl-be"      , 150 },
-        { L"nl-nl"      , 84  },
-        { L"nn-no"      , 151 },
-        { L"no"         , 19  },
-        { L"ns-za"      , 141 },
-        { L"pa"         , 54  },
-        { L"pa-in"      , 126 },
-        { L"pl"         , 20  },
-        { L"pl-pl"      , 86  },
-        { L"pt"         , 21  },
-        { L"pt-br"      , 87  },
-        { L"pt-pt"      , 152 },
-        { L"quz-bo"     , 140 },
-        { L"quz-ec"     , 159 },
-        { L"quz-pe"     , 168 },
-        { L"ro"         , 22  },
-        { L"ro-ro"      , 88  },
-        { L"ru"         , 23  },
-        { L"ru-ru"      , 89  },
-        { L"sa"         , 60  },
-        { L"sa-in"      , 133 },
-        { L"se-fi"      , 167 },
-        { L"se-no"      , 118 },
-        { L"se-se"      , 156 },
-        { L"sk"         , 25  },
-        { L"sk-sk"      , 91  },
-        { L"sl"         , 34  },
-        { L"sl-si"      , 100 },
-        { L"sma-no"     , 190 },
-        { L"sma-se"     , 195 },
-        { L"smj-no"     , 176 },
-        { L"smj-se"     , 184 },
-        { L"smn-fi"     , 203 },
-        { L"sms-fi"     , 199 },
-        { L"sq"         , 26  },
-        { L"sq-al"      , 92  },
-        { L"sr"         , 227 },
-        { L"sr-ba-cyrl" , 194 },
-        { L"sr-ba-latn" , 189 },
-        { L"sr-sp-cyrl" , 166 },
-        { L"sr-sp-latn" , 153 },
-        { L"sv"         , 27  },
-        { L"sv-fi"      , 154 },
-        { L"sv-se"      , 93  },
-        { L"sw"         , 51  },
-        { L"sw-ke"      , 122 },
-        { L"syr"        , 64  },
-        { L"syr-sy"     , 138 },
-        { L"ta"         , 56  },
-        { L"ta-in"      , 128 },
-        { L"te"         , 57  },
-        { L"te-in"      , 129 },
-        { L"th"         , 28  },
-        { L"th-th"      , 94  },
-        { L"tn-za"      , 110 },
-        { L"tr"         , 29  },
-        { L"tr-tr"      , 95  },
-        { L"tt"         , 53  },
-        { L"tt-ru"      , 124 },
-        { L"uk"         , 32  },
-        { L"uk-ua"      , 98  },
-        { L"ur"         , 30  },
-        { L"ur-pk"      , 96  },
-        { L"uz"         , 52  },
-        { L"uz-uz-cyrl" , 158 },
-        { L"uz-uz-latn" , 123 },
-        { L"vi"         , 39  },
-        { L"vi-vn"      , 105 },
-        { L"xh-za"      , 111 },
-        { L"zh-chs"     , 3   },
-        { L"zh-cht"     , 226 },
-        { L"zh-cn"      , 144 },
-        { L"zh-hk"      , 161 },
-        { L"zh-mo"      , 178 },
-        { L"zh-sg"      , 170 },
-        { L"zh-tw"      , 70  },
-        { L"zu-za"      , 112 },
-    };
-    // clang-format on
-
-    // This static_assert is case-sensitive, which is more than sufficient for the case-insensitive runtime lookups.
-    static_assert(_STD is_sorted(
-        _STD begin(LocaleNameToIndexTable), _STD end(LocaleNameToIndexTable), [](const auto& left, const auto& right) {
-            return _STD wstring_view{left.name} < _STD wstring_view{right.name};
-        }));
-
-} // unnamed namespace
-
-// __wcsnicmp_ascii
-// Implements wcsnicmp for ASCII chars only.
-// We can't use wcsncmp in this context because we may end up trying to modify
-// locale data structs or even calling the same function in NLS code.
-extern "C" int __wcsnicmp_ascii(__in const wchar_t* string1, __in const wchar_t* string2, __in size_t count) {
-    wchar_t f;
-    wchar_t l;
-    int result = 0;
-
-    if (count) {
-        // validation section
-        do {
-            f = static_cast<wchar_t>(__ascii_towlower(*string1));
-            l = static_cast<wchar_t>(__ascii_towlower(*string2));
-            ++string1;
-            ++string2;
-        } while (--count && f && f == l);
-        result = static_cast<int>(f - l);
-    }
-
-    return result;
-}
-
-// Maps input locale name to the index on LcidToLocaleNameTable
-extern "C" int GetTableIndexFromLocaleName(__in const wchar_t* localeName) {
-    const LOCALENAMEINDEX* localeNamesIndex = LocaleNameToIndexTable;
-    int bottom                              = 0;
-    int top                                 = _countof(LocaleNameToIndexTable) - 1;
-
-    while (bottom <= top) {
-        int middle    = (bottom + top) / 2;
-        int testIndex = __wcsnicmp_ascii(localeName, localeNamesIndex[middle].name, LOCALE_NAME_MAX_LENGTH);
-
-        if (testIndex == 0) {
-            return localeNamesIndex[middle].index;
-        }
-
-        if (testIndex < 0) {
-            top = middle - 1;
-        } else {
-            bottom = middle + 1;
-        }
-    }
-
-    return -1;
-}
+#include <yvals_core.h>
 
-// Maps input LCID to an index in LcidToLocaleNameTable
-extern "C" int GetTableIndexFromLcid(__in LCID lcid) {
-    int bottom = 0;
-    int top    = _countof(LcidToLocaleNameTable) - 1;
+#if _STL_WIN32_WINNT < _STL_WIN32_WINNT_VISTA
 
-    while (bottom <= top) {
-        int middle    = (bottom + top) / 2;
-        int testIndex = lcid - LcidToLocaleNameTable[middle].lcid;
-
-        if (testIndex == 0) {
-            return middle;
-        }
-
-        if (testIndex < 0) {
-            top = middle - 1;
-        } else {
-            bottom = middle + 1;
-        }
-    }
-
-    return -1;
-}
-
-// __crtDownlevelLocaleNameToLCID() - Maps the locale name to LCID on Windows XP.
-extern "C" LCID __cdecl __crtDownlevelLocaleNameToLCID(LPCWSTR localeName) {
-    int index;
-
-    if (localeName == nullptr) {
-        return 0;
-    }
-
-    index = GetTableIndexFromLocaleName(localeName);
-
-    if (index < 0 || index >= _countof(LcidToLocaleNameTable)) {
-        return 0;
-    }
-
-    return LcidToLocaleNameTable[index].lcid;
-}
-
-// __crtDownlevelLCIDToLocaleName() - Maps the LCID to locale name on Windows XP.
-extern "C" int __cdecl __crtDownlevelLCIDToLocaleName(LCID lcid, LPWSTR outLocaleName, int cchLocaleName) {
-    if (lcid == 0 || lcid == LOCALE_USER_DEFAULT || lcid == LOCALE_SYSTEM_DEFAULT) {
-        return 0;
-    }
-
-    if ((outLocaleName == nullptr && cchLocaleName > 0) || cchLocaleName < 0) {
-        return 0;
-    }
-
-    const int index = GetTableIndexFromLcid(lcid);
-    if (index < 0) {
-        return 0;
-    }
-
-    const wchar_t* const buffer = LcidToLocaleNameTable[index].localeName;
-    // the following cast is safe because LOCALE_NAME_MAX_LENGTH fits in int:
-    const int count = static_cast<int>(wcsnlen(buffer, LOCALE_NAME_MAX_LENGTH));
-
-    if (cchLocaleName > 0) {
-        if (count >= cchLocaleName) {
-            return 0;
-        }
-
-        wcscpy_s(outLocaleName, cchLocaleName, buffer);
-    }
-
-    return count + 1;
-}
+#include "awint.hpp"
 
 // TRANSITION, ABI: preserved for binary compatibility
 extern "C" _CRTIMP2 int __cdecl __crtCompareStringEx(_In_opt_ LPCWSTR lpLocaleName, _In_ DWORD dwCmpFlags,
@@ -641,4 +27,4 @@ extern "C" _CRTIMP2 int __cdecl __crtGetLocaleInfoEx(_In_opt_ LPCWSTR const lpLo
     return GetLocaleInfoEx(lpLocaleName, LCType, lpLCData, cchData);
 }
 
-#endif // _STL_WIN32_WINNT < _WIN32_WINNT_VISTA
+#endif // _STL_WIN32_WINNT < _STL_WIN32_WINNT_VISTA
diff --git a/tests/std/tests/Dev11_1086953_call_once_overhaul/test.cpp b/tests/std/tests/Dev11_1086953_call_once_overhaul/test.cpp
index 27338bff59b..35c969fc237 100644
--- a/tests/std/tests/Dev11_1086953_call_once_overhaul/test.cpp
+++ b/tests/std/tests/Dev11_1086953_call_once_overhaul/test.cpp
@@ -52,17 +52,7 @@ void ThrowingFunc(int* const p) {
     }
 }
 
-// ***** Machinery to test the XP codepath: *****
-// extern "C" {
-//     extern void * __encodedKERNEL32Functions[40 /* eMaxKernel32Function */];
-//     extern uintptr_t __security_cookie;
-// }
-
 void run_tests() {
-
-    // ***** Machinery to test the XP codepath: *****
-    // __encodedKERNEL32Functions[5 /* eInitOnceExecuteOnce */] = reinterpret_cast<void *>(__security_cookie);
-
     // Basic check.
     {
         once_flag flag;
diff --git a/tests/std/tests/P0218R1_filesystem/test.cpp b/tests/std/tests/P0218R1_filesystem/test.cpp
index 0ff4f084c32..ef6d08aea10 100644
--- a/tests/std/tests/P0218R1_filesystem/test.cpp
+++ b/tests/std/tests/P0218R1_filesystem/test.cpp
@@ -952,19 +952,11 @@ void check_symlink_permissions(const error_code& ec, const wchar_t* const functi
         pass = false;
     }
 
-#ifdef WINDOWS_XP
-    if (ec.value() != 50) {
-        wcerr << L"Expected ERROR_NOT_SUPPORTED from " << function_id << L" but it returned " << ec.message().c_str()
-              << L"\n";
-        pass = false;
-    }
-#else // ^^^ WINDOWS_XP ^^^ // vvv !WINDOWS_XP vvv
     if (ec.value() != 1314) {
         wcerr << L"Expected ERROR_PRIVILEGE_NOT_HELD from " << function_id << L" but it returned "
               << ec.message().c_str() << L"\n";
         pass = false;
     }
-#endif // WINDOWS_XP
 
     wcerr << L"Warning: could not test " << function_id
           << L" due to symlink creation failure, do you have admin rights?\n";
@@ -1565,12 +1557,7 @@ void test_canonical() {
 
     // test that canonical on a directory is not an error
     (void) canonical(L"."sv, ec); // == canonical(current_path())?
-#ifdef WINDOWS_XP
-    EXPECT(ec.value() == 50 /* ERROR_NOT_SUPPORTED */);
-    EXPECT(ec.category() == system_category());
-#else // ^^^ WINDOWS_XP ^^^ // vvv !WINDOWS_XP vvv
     EXPECT(good(ec));
-#endif // WINDOWS_XP
 
     // test that canonical on an ordinary file returns that file's DOS path
     const auto filename = L"test_canonical.txt"sv;
@@ -1578,10 +1565,6 @@ void test_canonical() {
     EXPECT(good(ec));
     create_file_containing(L"test_canonical.txt", L"Hello world\n");
     const path p(canonical(filename, ec));
-#ifdef WINDOWS_XP
-    EXPECT(ec.value() == 50 /* ERROR_NOT_SUPPORTED */);
-    EXPECT(ec.category() == system_category());
-#else // ^^^ WINDOWS_XP ^^^ // vvv !WINDOWS_XP vvv
     EXPECT(good(ec));
     const auto& text = p.native();
     assert(text.size() > filename.size() + 1);
@@ -1589,7 +1572,6 @@ void test_canonical() {
     const auto diffSize = static_cast<ptrdiff_t>(filename.size());
     EXPECT(*(text.end() - diffSize - 1) == L'\\');
     EXPECT(equal(text.end() - diffSize, text.end(), filename.begin(), filename.end()));
-#endif // WINDOWS_XP
     EXPECT(remove(L"test_canonical.txt", ec));
     EXPECT(good(ec));
 }
@@ -3193,7 +3175,6 @@ void test_lexically_proximate() {
 }
 
 void test_weakly_canonical() {
-#ifndef WINDOWS_XP
     error_code ec;
 
     create_directories(L"test_weakly_canonical/a/b/c"sv, ec);
@@ -3277,7 +3258,6 @@ void test_weakly_canonical() {
 
     remove_all(L"test_weakly_canonical"sv, ec);
     EXPECT(good(ec));
-#endif // WINDOWS_XP
 }
 
 void test_remove() {
@@ -3511,9 +3491,6 @@ void test_permissions() {
         EXPECT(good(ec));
         // try to make the symlink target not readonly
         permissions(linkname, perms::all, perm_options::replace, ec);
-#ifdef WINDOWS_XP
-        EXPECT(bad(ec)); // missing SetFileInformationByHandle
-#else // ^^^ WINDOWS_XP ^^^ // vvv !WINDOWS_XP vvv
         EXPECT(good(ec));
         // symlink unchanged:
         EXPECT(symlink_status(linkname).permissions() == readonlyPerms);
@@ -3521,7 +3498,6 @@ void test_permissions() {
         // target changed:
         EXPECT(status(linkname).permissions() == perms::all);
         EXPECT(good(ec));
-#endif // WINDOWS_XP
     }
 
     permissions(linkname, perms::all, perm_options::replace | perm_options::nofollow, ec);