It's XP
I assume it's up to date--my updates are automatic. I almost typed "service pack 2," but honestly, I don't even know where to find that information.
Over the past 24 hours, it has become more stable and I haven't lost anything. I think I overdid my cleanup of temp files and might have removed some file that set preferences, but so far, everything appears to be intact. I keep getting an email from someone claiming there is an ebay payment dispute. I just delete these normally, but yesterday, I wanted to see what the complaint was, so I opened one and immediately got a virus bulletin that the page I was trying to load had some malware in it. I may have accidentally allowed some third party into my trusted zone--I froze them out and appear to be functioning normally. So I apologize for suspecting CCleaner--you always suspect the last thing you loaded, but in fact, I loaded CCleaner because I was having problems I couldn't account for. CCleaner probably clearned up the mess and here I was blaming it.
Apologies. If I experience the problem again, I will fill you in on as many of the details you've requested as I can find.