Just wanted to post my joy at achieving something i thought would be hard but turned out to be as easy as it claimed:
I had a Windows XP (neither SP1 nor SP2) disc, and knew that i was going to be upgrading my system to SATA (see 'My System' for my shiny new Opteron - Yay!). I also heard that older XP discs dont install (at least easily) onto SATA drives, you need PATA.
Then i read about NLite (currently RC6), that will slipstream an older disc into a newer one and do other fancy stuff too. Having once before turned a Windows 2000 disc into a 2000 SP2 disc which was do-able but a hassle, Nlite was a miracle. I put the service pack on, even added a number of post-SP2 updates, and had the option (but didnt) integrate updated drivers. I may in fact do another one with the newer drivers on board.
Such a marvel, as the advert says "It does what it says on the tin".
Check it out!