Well, there goes the rest of the night.
Many thanks to M. and her dad for getting my box back into working shape. The weirdness: while the system restore was from yesterday, my Firefox bookmarks are reset to at least six months ago, if not more. No idea on that one.
Oh, and while I was waiting for the cleanup to complete (which took hours,), I totally passed out hugging the cat, who was totally passed out on the bed. She's wily, that one.