I previously had a 2007 iMac in which I had a windows XP partition through bootcamp. Now I recently upgraded my machine to a Mac Pro. I erased the original iMac hard drive and just reinstalled OS X and wiping out the windows partition before giving it to my parents. Now I want to use one of the 4 drives in my Mac Pro as a windows drive. Do I have to go out and purchase a new copy of windows 7 or can I legally reinstall windows XP for now even though it was already installed on my old machine? Thanks