This is baffling and really annoying.

I installed BIAB on an external drive, following Andrew's advice here:

https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=573850&page=2

Worked fine until just now.

I was using BIAB 2020 on a simple project. Worked fine, then froze; then I got a Windows "oops something went wrong" message, did some kind of count to 100%, after which the PC shut itself down.

When I rebooted, BIAB would not launch at all (neither 32 bit nor 64). Their icons were replaced by the generic icon Windows uses when it doesn't recognise a file association. Same applies to my SGU files. Clicking on them causes Windows to ask me what program to use.

Then I checked my external drive's BB folder. Gone! Not even in the recycle bin.

Never seen anything like this.

I'm on Windows 10 Pro

Any advice?