I'm having a similar problem with yours. I have 2 WD Raptors, and I have installed Windows XP successfully and been using for a week also. This morning, I found my system freezed and tried to reboot, then I got the BSOD.
So I went in the BIOS to see what's wrong, and my 2nd HD was missing. (C: is still there) When I tried to boot the OS, the system froze on Windows logo screen. It's the second time that this has happened to me, and at first I replaced the HD.
I tried to Safe boot, and it freezes after Mup.sys! I've been puzzled all day. (couldn't check it thoroughly since I'm at work right now)
Are you using SATA? I'm thinking it's one of the followings:
1. Faulty Hard Disk
2. Faulty SATA Cable (or loose SATA/Power cable)
3. Faulty SATA Ports on ASUS motherboard
Could anyone help us out? I've been very happy with this AMD system since I switched from Intel, except this problem.
Thanks alot
lop