So I reformatted my drive to hybrid gpt. Here's the process I accidentally fell upon. -
I formatted the drive in OS X to gpt, created two partitions (Fat 32 and Mac Journaled) then rebooted and installed windows XP from the Windows install CD to the first partition. I let XP reboot during install, then got the normal error message that there was no boot drive. I rebooted to my NBI setup USB stick and installed SL to the second partition, running all the normal procedures.
I rebooted, and the Chameleon bootloader ran, I selected the XP partition, and the XP install continued like a normal XP install. I didn't have to run diskpart, or anything like that. Now everything works just fine. FY I, openGL runs significantly faster in SN than XP