JudasIscariot: Ebay.com has the answer, or if you want something within the EU, then ebay.co.uk ought to fit the bill :)
Windows 7 on ebay.com phaolo: Thank you, but.. are those really safe?
I read about a lot of scams with copied software or cracked keys.
Look for the picture of an actual box along with a picture of the license sticker. Look at the seller's feedback and, if you do decide to go via ebay, keep all receipts and report the seller and the item as pirated/cracked not legit. AFAIK, ebay should have a strict policy regarding illicit software so you should be covered on that front as well.