You cannot use any xp professional and the key from the dell computer. different install disks have different keys they are valid for. in order to use the key from the computer, you must have a dell oem install disk. there is a work around, though. I use a retail version of the install disk to do the initial setup. Microsoft has a key update utility that I use to change the key to the one on the coa after the setup is complete. one positive is you don't end up with all the dumb preloaded stuff that it came from the factory with.