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 a opaque black color scheme.
 * Search has been improved with the addition of a text box.
 * The Security and Maintenance flyout has been removed.

Cortana
This is the first available build to include Cortana, which was a featured brought over from Windows Phone. It can be accessed from taskbar search.

Settings

 * Settings has an updated homepage, which resembles the Category View in Control Panel.
 * Background settings have been added to personalization.
 * An option to change feedback frequency has been added.
 * Speech now has an option to change your spoken language.
 * The Storage Sense and Windowing pages have been added.
 * Buttons for full-screen dialogs (ex: Refresh your PC) have been made wider.

Windows Update
Windows Update has been removed from Control Panel. However, it can be restored by modifying registry keys.

Miscellaneous

 * The privacy page during the OOBE has been updated.
 * New desktop wallpapers and themes are included.
 * The window design of Metro applications has changed to a more modern style.
 * The "Welcome to Tech Preview" desktop shortcut has been removed.
 * The Settings section on the Charms bar has been removed.

Hidden features
The following hidden features have been found within this build:


 * New tray clock user interface - enabled by creating key  under
 * Hidden lock screen - enabled by setting  to 1 under
 * XAML Start menu - set  to 1 under
 * New volume flyout - enable by setting  to 1 under

Hidden apps
There are a few hidden apps in this build:


 * Windows Default Lock Screen - accessed by running
 * Cloud Experience Host - accessed by running
 * Print Dialog - accessed by running
 * Windows Shell Experience Host - accessed by running

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

Incorrect window thumbnail border color
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.