Linux in Windows
Whilst I prefer doing it the other way around, i.e. running windows in Linux (not that I ever use Windows anyway), but I guess there are instances when you are forced to use Windows (specially in the corporate environment) but prefer using Linux as your main desktop. In this case, this beginner's guide might be able to help you run Linux in Windows.
The guide requires VMWare, but you can use Parallels do this as well, to run Fedora, Ubuntu, Suse, Damn Small Linux or Puppy Linux.
Personally, I'd rather that you run Windows in Linux instead – it is much, much safer.
[image courtesy of osde.info]