Reinstall XP-Pro to be able to activate

Was unable to install service pack 1 in a computer I bought so I purchased a full version of XP-Pro and want to know how to install it to be able to activate and register without doing a clean install if possible. Can I do a full install over the old version, or do a repair install?

 

You said that you bought a computer with WinXP installed, and that you couldn't install SP1. What error messegages were shown why it didn't install? You may have bought a computer with a copy of "the Devils Own" installed. Download a utility such as Rock XP - Major Geeks has it for download - and view your CD key. If it is one of the ones that Microsoft blacklisted in SP1, then that is your problem. I'm with the Major, in that I have no idea of what problems that you will have on a repair install.
If your original program was a corporate version, then I'm almost certain that a regular XP Pro key wouldn't work to activate it. Follow the Major's advice, and I can sympathize with your problem.