That hiccuping I mentioned yesterday? Video card. Phizzziittt. I also suspect it was the source of the vague scent of burning. sigh One of the things I didn't upgrade the last time.
All I can say is that it's had a long, fruitful and useful life; it should have enjoyed retirement somewhere, but no - I had to work it to death.
I'll take it to the shop next week. So much for the end of the month deadline I set for myself.