Windows 10 build 9780

Windows 10 build 9780 is a pre-Technical Preview build of Windows 10, which was uploaded to BetaArchive on 26 January 2019. It is currently the earliest available build of Windows 10, and due to its earliness it is identified as Windows 8.1 in many areas and still has kernel version 6.3. Despite having a start menu, native support for Windows Store apps in windowed mode hasn't been introduced yet by default.

Window animations
DWM-based window animations (particularly window open and close) have been changed to simpler transitions.

Start menu
A new start menu has been introduced, merging the Windows 8 and Windows 7 styles.

Home page in File Explorer
File Explorer received a new page called Home, it opens when you launch the app.

Wallpapers
and  wallpapers have been swapped, resulting in Windows 8.1's   becoming the default wallpaper.

Timebomb
Like other Windows 10 builds found in the  branch, this build contains a non-functional timebomb and as a result can be installed on the current date.

Metro live colorization
Usually, Metro picks a different color from the wallpaper than Aero.

Window thumbnail color error
Window thumbnails on the taskbar do not change color, but the user can change it after the computer restarts.

Safe Mode
Trying to boot into Safe Mode (whether via msconfig or Recovery Options) results in a black screen.