I puzzle around a while and decide to try motherboard replacement. Grab an Asus A7N8X-X. These rule, by the way. Super cheap, perform speedwise within a few percent of the more expensive boards, and 100% stable.
Motherboard makes everything work again. So do a 'repair' install of XP to get new motherboard recognized. Then the real fun begins. Somehow they have gotten this machine infected with every backdoor, spyware, malware, annoying browser applet in the known universe. I use a combination of Adaware and AVG anti-virus to try and clean it.
I have to run these things REPEATEDLY to try and get shit locked down. I have to go spelunking through windows directories and google for suspicious-looking filenames to delete. I think I've kind of got things locked down but man, i should be getting big bucks for this stuff.