I remember reading a thread on Swedish computer forum.

There was a guy who had "compressed" his whole media livrary and saved it to a floppy disk, reinstalled his computer and now wanted to restor the media files....

Yeah, what he had done was to misunderstand what an MD5 hash was, he thought it was an extremely efficient compression algorithm....

And this is one of the many reasons I tell people that "an untested backup does not exist"

Ow.