IC7 will not boot XP SP2

I've been trying to apply SP2 (probably won't after this weekend), but it won't get past the XP splash screen on reboot. The system hangs, then reboots and continues this cycle. Ive gone back and reinstalled a base OS + SP1 and drivers only, and I get the same problem. Anyone seen this before?

- Got the latest BIOS?
- Clocked down to stock speeds?

Bios fixed it.