Virtualise it and flashback to earlier vm when it borks
I thought of doing that but then I have to teach people how to use a VM. It's not hard, but for the average user it probably would be, that and there's overhead, especially on an already slow computer.
Whenever I format a machine I keep an image of it though, but still a pain having to reconfigure their email, bookmarks, etc.
Ended up being able to just clean it up though, had a lot of spyware, and even after clearing it it was bloody slow, turns out skype was slowing it down and he did not need it so got rid of that. Then realized UAC was also slowing it down, whenever it would prompt for something instead of prompting right away it would take bloody ages to prompt and cause everything to lock up, so I brought it down a notch. Really I probably could have just outright disabled it, considering all the spyware there was, UAC is obviously useless. People just hit yes anyway. After those two things it sped it up. For him it was super fast so if he's happy then I'm happy. I'm probably use to my own machine with a SSD too so it seemed way slower for me than to him.