Windows 8 build 7973 (fbl core1 kernel npc)

Windows 8 build 7973 (fbl core1 kernel npc) is a build of Windows 8. This build updates the boot screen to the fish from the background of Windows 7's pre-release versions with the spinning circles seen in later builds (albeit at a larger size). It was leaked on 19 September 2015 by OSBetaArchive.

Redpill
A tool named Redlock can be used to unlock all of the Redpill levels on this build, including the Start screen.

With this build, the Start screen is beginning its evolution away from the Milestone 2 look of the previous builds. The design for the tiles on this build has changed to a look that more closely resembles the final. The Immersive Control Panel has also been redesigned, along with the splash screen for MS Help being changed to a rather crude one done in Microsoft Paint.

The Metro folder icons and thumbnails seen in build 7963 have been disabled.

Aero
This build appears to have a slightly broken Windows Aero theme, with only the top portion of the window frame using the blur effect, leaving the side borders transparent.

DWM
After installing the video card driver, Immersive Control Panel will open after using Ctrl+Shift+F9. It won't close unless you press Ctrl+Shift+F9 again.

Aero Glass in Starter and Home Basic
This build automatically enables Aero Glass transparency even when installing the Starter or Home Basic SKUs, which is not supported by default. However, changing the color scheme (visual style) to another one and then back to the default one will disable Aero Glass.