I was told by a lady working at the university software distribution center that if I needed to install Windows on my Mac that I could do so by only purchasing the Windows XP Pro upgrade and that I didn't need to buy and install the full-version of the OS (which they do not sell). Said something like, "you don't need the full-version, the upgrade will build upon the Mac OS that is already installed." However, BootCamp repeatedly instructs that you need the full-version Windows XP OS. I feel like this is too good to be true. Can someone clarify, before I unwrap my Windows XP Pro Upgrade and am not able to return it? thanks.