I don't think my desktop has been formatted since it was upgraded just over a year ago.
My laptop was formatted (restored) as soon as I got it back home. See, often when you buy computers in Thailand, they immediately fill it with pirated software like Windows, Office, and just about everything else. While my laptop did come with an authentic version of Vista, they had stuck a bunch of other crap on it while they were "checking" it. Needless to say the system was all screwed up by the time I got it, so as soon as it was out of the box and powered on.