PSU Failure?

I've been troubleshooting my friends computer for a while and I thought I had all my problems solved when ASUS repaired the motherboard. However, this is not the case. I received the motherboard back and the computer is still unstable. I've tried the memory in my computer and it checks out ok. I ran the extensive Western Digital Test on the hard drive, and that checked out ok. The processor is fine, and everything else in the case was disconnected when I had these problems.

The computer will restart out of nowhere, especially when I access the control panel, and some times it will not even boot and crash at the windows screen. I've tried two fresh installs but I still have the same problem. Some of the ports on the back of the motherboard are unresponsive (PS/2 keyboard as an example) and this has been one major pain in the A$$.

Could my PSU be failing? I mean it makes sense that the computer would restart when ever more power is needed from a running drive or what ever, and the unstable power could explain why most of the motherboard ports don't work.

I am completely out of ideas here. Can anyone save me?

Thanks in advance.

cooked

ASUS A7N8X-VM/400 Socket A
Anthlon XP 2000+
2X256 CORSAIR Value Select PC3200
WD 80GB HDD
Integrated Graphics
FRESH install of Windows XP SP2 Pro / Drivers
No other programs

 

Hopefully you can borrow someone elses power supply for a test
process of elimination

 

Unfortunately most of my friends aren't computer savvy enough to let me take out their PSU lol. But I did tear apart my rig, which was frustrating and messy, but it seems the PSU was the culprit here. Surprisingly, the computer boots 10X faster with my PSU in it and has remained stable so far. I'm going to order a new one as soon as I collect some money from my buddy. This should solve my problems.