docs: give RetroArch's Windows system folder

RetroArch defaults system_directory to :\system, the folder of retroarch.exe (platform_win32.c), for the installer as for the portable archive. %APPDATA%\RetroArch holds only a fallback retroarch.cfg.

tests/test_doc_pages.py

@@ -726,5 +726,22 @@ class FirstInstallWalkthrough(unittest.TestCase):
         self.assertNotIn("cannot stop and ask", section)
 
 
+class RetroArchWindowsSystemFolder(unittest.TestCase):
+    """Getting started gave %APPDATA%\\RetroArch\\system for the Windows
+    installer. RetroArch's default is `:\\system`, the folder of
+    retroarch.exe (platform_win32.c). %APPDATA% is where a retroarch.cfg
+    can live, and install.py reads it there."""
+
+    def test_page_and_installer_agree(self):
+        import install
+
+        source = inspect.getsource(install)
+        self.assertIn('ra_dir or exe_dir / "system"', source)
+        self.assertTrue(str(install._os_default_dests("windows")["retroarch"]).replace("\\", "/").endswith("/system"))
+        section = _section(_page("getting-started.md"), "RetroArch")
+        self.assertNotIn("%APPDATA%\\RetroArch\\system", section)
+        self.assertIn("`system\\` next to `retroarch.exe`", section)
+
+
 if __name__ == "__main__":
     unittest.main()

wiki/getting-started.md

@@ -108,18 +108,19 @@ RetroArch uses the `system_directory` setting in `retroarch.cfg`. Default locati
 
 | OS | Default path |
 |----|-------------|
-| Windows (installer) | `%APPDATA%\RetroArch\system\` |
-| Windows (portable .7z) | `system\` next to `retroarch.exe` |
+| Windows (installer or portable .7z) | `system\` next to `retroarch.exe` |
+| Windows (UWP/MSIX package) | `%LOCALAPPDATA%\Packages\1e4cf179-f3c2-404f-b9f3-cb2070a5aad8_*\LocalState\system\` |
 | Linux | `~/.config/retroarch/system/` |
 | Linux (Flatpak) | `~/.var/app/org.libretro.RetroArch/config/retroarch/system/` |
 | macOS | `~/Library/Application Support/RetroArch/system/` |
 | Steam Deck (Flatpak) | `~/.var/app/org.libretro.RetroArch/config/retroarch/system/` |
 | Android | `/storage/emulated/0/RetroArch/system/` |
 
-Windows has two layouts because the installer stores its data under `%APPDATA%`
-while the portable archive keeps everything inside the folder you extracted it
-to. If both exist on the machine, the one RetroArch actually reads is the one
-shown in the UI.
+On Windows, `retroarch.cfg` is read beside `retroarch.exe` first, then from
+`%APPDATA%\RetroArch\`. Either way, a `system_directory` left at its default is
+the `system` folder beside `retroarch.exe` (`:\system` in RetroArch's
+`frontend/drivers/platform_win32.c`, where `:` stands for the folder of the
+executable).
 
 To check your actual path: open RetroArch, go to **Settings > Directory > System/BIOS**, or look for `system_directory` in `retroarch.cfg`.