All the Windows discs have a key or code of some kind (I remember searching for these when I was wanting a beta version of 7). It's a long jumble of letters and numbers, it's called a check code or something. If you search for that you'll find loads of torrent links, but I don't know where to find the code
Someone like Nekro should be able to help you there. He's very clued up on most things PC.