Worst security cleanup?

nakhla writes: Last night, I was tasked (by my wife) to help fix her friend's computer. It is a Windows XP home system which has been running slowly, almost to the point of unusability. (I'm sure *that's* never happened before) It turns out that hundreds of random processes had filled up its meager 256 MB of RAM. The cause? Nearly 7,500 viruses and worms that had infected the system. That number doesn't even include the hundreds of spyware and adware programs that had installed themselves, as well. Although the box is now behind a firewall, that wasn't always the case. This was, by far, the most infected system I'd ever seen, but I'm sure it can't be the worst ever. What was the worst security cleanup you ever had to perform?