Well, I am not using x64 XP-SP2. I am using the 32 bit version. And, I am on a MacBookPro17 laptop with a built-in hard drive. I know that the information you mentioned worked on my MacPro box.
I have successfully installed Win XP-SP2 behind Leopard using bootcamp 2.0. Here's the run down...
First of all, this is like the 5th try. After turning the system off/on several times and retrying, it finally went. Here's how you do a fresh install...
1) Leopard is installed using the entire internal disk. (disktool available on
the DVD when it is booted if needed)
2) BootCamp 2.0 is used to partition the internal HDD. (32MB works)
3) Insert XPSP2 CD when prompted to continue.
4) Go through the XP text menus to install onto the partition BC created.
5) DO NOT QUICK format. Do a full format on the BC partition in FAT(32).
6) Windows will install and reboot.
7) When system comes back up do not hit 'any key' to boot CD. Let HDD boot.
8) XP finishes installing.
9) When all that is done, pop ur Leopard DVD back in and it will ask to install
BC drivers. Click yes/continue. System will reboot again.
10) Now XP should be installed and all Mac hardware working.
That's the best way I found to do this on a MacBookPro Laptop.
On a desktop you can just boot XP CD (OPTION KEY at boot time) and install it to another HDD in the system. For some reason, if you want to put XP on the same HDD as OSX, you have to use BootCamp, otherwise is not needed.
Thanks again,
Scott