Some time ago I purchased XP Home Upgrade for an older PC. Now I would like to use that same disk to put XP on my new MacBook Pro, will that work? Thanks
No, it won't work. You need to purchase XP SP2. Boot Camp will not install from an XP SP3 disk. You need to install XP SP2, then install Boot Camp 2.1 in Windows (it is a Windows executable), then upgrade XP SP2 to SP3 via Windows update. This has been covered in other threads - at present, Boot Camp requires an XP SP2 disk.
Cheers
What apparently can't be done is install it under BC using a single-disc, XP SP3 retail disk. You can see this thread: http://www.mac-forums.com/forums/windows-classic-linux-other-os/135758-xp-sp3-problem-install.html
Cheers