Windows NT 3.1 build 175

Windows NT 3.1 build 1.175.1 was shown during Windows World 91. It is the earliest known build of Windows NT. Bill Gates himself demonstrated the new multitasking capabilities that were set to be introduced with Windows NT. The build number can be seen at the top of the video from 0:20 onwards. The full string is believed to say "NT 32-bit Windows [NTX86BLD] v1.175".

Bill Gates first uses the new File Manager (ported to NT from Windows 3.0) to launch the Clock application, then minimizes both (along with Program Manager) to reveal two instances of WINBez running in the background, along with another graphics demo app named simply "Demo".