Wheely34

I was working on my buddy's desktop today. He was complaining that the computer would keep shutting off. I used the computer and what happens is the monitor keeps shutting off (losing signal) but the computer stays on. Sometimes the monitor would turn off, come back on again, and the computer would restart itself. I originally thought it was a video card issue, but that wouldn't explain the re-booting. I then tried a known working video card and experienced the same issues. I then thought maybe some of the system files got corrupted, so I figured I would just reformat his computer and reinstall his OS to see if that would fix it. When i tried to reformat (OS is XP Home) windows could not recognize an HDD and basically was telling me there was no HDD installed. I then noticed on startup that i was getting a very quick error message saying:

Serial Device_CH0 Master: WDC WD1600JD-00HBB0
Serial Device_CH1 Master: No Device

Now I know it is either an issue with his motherboard, or his HDD. Weird thing is, the computer does boot into the OS and things can be saved to the HDD, so I can't figure out what is going on with this thing.

He has an ASUS K8V-X motherboard with a Socket 754 Athlon 64 processor. I did run a virus scan and it came back negative. I think there is a hardware issue with his motherboard...am i correct?? Or could it be his HDD?