Open notepad, and grab the cody below here.
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Themes\InstalledThemes\MCT]
"%windir%\\Globalization\\MCT\\MCT-AU\\Theme\\AU.theme"=""
"%windir%\\Globalization\\MCT\\MCT-CA\\Theme\\CA.theme"=""
"%windir%\\Globalization\\MCT\\MCT-DE\\Theme\\DE.theme"=""
"%windir%\\Globalization\\MCT\\MCT-GB\\Theme\\GB.theme"=""
"%windir%\\Globalization\\MCT\\MCT-JP\\Theme\\JP.theme"=""
"%windir%\\Globalization\\MCT\\MCT-US\\Theme\\US.theme"=""
"%windir%\\Globalization\\MCT\\MCT-ZA\\Theme\\ZA.theme"=""
[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Wallpapers\0\KnownFolders\Windows Wallpapers\MergeFolders]
"%windir%\\Globalization\\MCT\\MCT-AU\\Wallpaper"=""
"%windir%\\Globalization\\MCT\\MCT-CA\\Wallpaper"=""
"%windir%\\Globalization\\MCT\\MCT-DE\\Wallpaper"=""
"%windir%\\Globalization\\MCT\\MCT-GB\\Wallpaper"=""
"%windir%\\Globalization\\MCT\\MCT-JP\\Wallpaper"=""
"%windir%\\Globalization\\MCT\\MCT-US\\Wallpaper"=""
"%windir%\\Globalization\\MCT\\MCT-ZA\\Wallpaper"=""
"Save as" and change its extension from
.txt to be
.reg as the registry command, then open its file and accept the option on the popup window.