Please also note that there is currently NO WAY to eject the Windows XP CD during install to insert the older disc. Upgrade CDs are completely useless for use with Boot Camp.
Yes, I tried, just to make sure. (I had an SP2 upgrade disc, and a no-SP full install disc, I ended up having to create my own SP2 full editon using a technique called 'slipstreaming'.) It asks you to insert the old Windows disc, but you have no way of swapping discs. (The Eject keyboard key doesn't work until you install the drivers, and there is no 'emergency eject hole' on the MBP, iMac, or mini.)