Need help slipstreaming XP Pro with SP 2 and updates…

I have a simple question, and I’m hoping the answer is just as simple… Though I don’t really expect that…

I am attempting to, as I said in the title, slipstream XP Pro with SP 2 and relevant updates, but the only copy of XP I have has SP 1 integrated. Nlite is telling me that I need to remove SP 1 before I can proceed, but I don’t know how to do that… Any ideas?