Windows 10 build 9900

Windows 10 build 9900 is a build of Windows 10, which was uploaded to BetaArchive on 29 January 2015.

It is the earliest available build of Windows 10 to be compiled in the  branch.

Taskbar

 * The taskbar design has been changed to a flatter style and now uses the black color seen in the RTM.
 * Taskbar search has been improved with the addition of a text box.
 * Security and Maintenance icon on the taskbar has been removed.

Cortana

 * Cortana has been added.

Windowed Metro

 * The window design has changed to a more modern style.

PC Settings and the Control Panel

 * PC Settings has an updated homepage.
 * Update Center has been removed from Control Panel.

Charms Bar

 * Charms bar received a minor update.
 * Settings section has been removed from it.

Desktop

 * The "Welcome to Tech Preview" desktop shortcut has been removed.

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