I have a current operating system of an oem xp media center, but most of the music recording software and hardware I wish to add (or already have) are incompatible. I wanted to change to xp pro, but when I enter the product key from the back of the xp pro (SP2) folder, I get "invalid product key". I once used the disk to upgrade an old computer that is now defunct. Can't I use it on a a media center computer? Or do I have to do a clean install?