So... the reformatting to RAID 0 worked and WinXT installed. So I deleted the RAID 0 configuration in BIOS, set it back to RAID 1, and re-installed windows, using a full format.
Looks good. Everything works, and the annoying beep I was getting from the case speaker has stopped. Have managed to get Zone Alarm, AVG, and Spyware Blaster running with no problems.
The big ordeal (for me) will be getting Steam up and running. I'll be keeping my fingers (and toes) crossed!