That might be MinWin, which is really just a core used to build Windows products since Vista. It is not a standalone OS though Microsoft has demo'd MinWin with just enough extra stuff to run a simple web server.

I'm not convinced it even includes kernel32 based on Mark Russinovich: Inside Windows 7.


People commonly add the VB6 runtime components to WinPE builds as it is. Lots of install-prep tools are being written in VB6, including ones to add a GUI Shell to WinPE.