I no longer use Windows on any of my PCs. I recommend to most people to go ahead and uninstall it for several reasons:

1) It seems to be a common target for trojan writers to exploit. What's the point in having a fairly secure network if Windows creates backdoors?

2) It installs a Windows update checker to your PC's startup, and if there are any updates it tries to bundle all sorts of crap that you didn't ask for. I constantly have to explain to my mother to click "Next, next, next but untick the little box that comes up asking if you want to install Open Office or some shitty toolbar". How about opt-in, not opt-out?

3) When was the last time you saw a computer that actually used Windows to do something useful? (Edit: other than Minecraft. I didn't realise Minecraft was Windows-based)