Windows 10 build 9901

Windows 10 build 9901 is a build of Windows 10, which was uploaded to BetaArchive on 14 December 2014. It is very similar to build 9900.

XAML Start menu
To enable the hidden start menu introduced in build 9900. Go to the following registry key:, create a DWORD value and name it   and set its value to 1, then log out and log in back.

UEFI BIOS
This build can only be installed on machines utilizing UEFI firmware since it hangs on a Legacy system.

Window thumbnail border color error
If window auto-colorization is enabled, the window thumbnail borders on the taskbar do not change color even after the wallpaper changes. This issue can be remedied by manually changing the window color through the Control Panel or restarting Windows.