[Nulyanna]

This problem was first noted when I booted into safe mode in an attempt to remove AVG Free. After about 10 minutes in safe mode, the computer just powered off. No BSOD, no shutdown sequence.... it was as if the computer had been unplugged from the wall. Upon reboot, it behaved normally, and allowed me to again enter safe mode. However, after about another ten minutes, the same thing happened. I booted into 'normal' mode, where everything until this point had been working fine - but the problem seemed to have carried over, in a way.

The pc can sit for as many as 10 hours, with the desktop and screensaver, no applications, and run just fine. But as soon as I try to play a game (usually WoW), *blink* gone - as if the power had been unplugged. Sometimes it will boot up normally again, sometimes it will fail on the Windows loading screen. When it fails on the loading screen, at the next boot, it will show the 'windows did not start normally' screen with selections. I have chosen "last known good config" as well as "boot normally" neither of which seem to have any effect.

My system:
Windows XP, all critical updates (and SP2) applied except for explorer - I prefer firefox.
Mainboard: MCP6P M2+ (supports my AMD Athlon 64 dual core)and has 4 SATA ports
Memory: 2 1G sticks of DDR2
Graphics card: GeFORCE 8400GS (PCI-X)
Hard Drive: SATA 200gig
Disc Drive: one CD/DVD ROM
Power Supply: 400W Wintech ATX (model # on case: WIN-400ps)

What I have done to troubleshoot so far:

After reading somewhere that there may be a problem with Windows, causing it to fail in safe mode, I physically removed the 200G drive, and replaced it with a fresh 320G - did a clean install of Windows, and all the updates. This did not solve the problem, and seemed to me to rule out a software issue.

Thinking that it may be a lack of power problem, and knowing that the graphics card wants 300W, I removed the graphics card from its slot, and plugged the monitor straight to the motherboard. This did not solve the problem.

I then unplugged the CD/DVD drive - both the power and IDE cable. This did not solve the problem.

I should mention, that everything gets blown out with canned air about once a month, so the power supply looked clean, but I thought I'd open it up anyway just to see.... and found a capacitor that was oozing! AAK! I went out and got a new 450W ISO supply (model ISO-500D), installed it, booted up, ran for maybe 2 hours, and *blink* same thing. Just as if the power cord had been yanked out of the wall. The amount of time the pc would stay on rapidly deteriorated after that - and within three reboots, I was back to the 'less than ten minute rule'.

I'm pretty sure it's not an overheating problem - I can place my hand on all the heat sinks in the pc, and they're barely warm to the touch.

I have inspected the motherboard - nothing in the circuitry looks fried, and all the capacitors look normal.

This was a custom built machine; the board listed above was new in January of this year, not the original board that came with the pc. The original board had an AGP slot for the graphics card, but both board and card had to be replaced when the fan on the graphics card went out and subsequently fried the board. The place that built it gave me nothing but hassle when that occurred and I'm reluctant to hand it back over to them again to be fixed. (they're the ones that installed AVG Free - without my knowledge or consent!!! I do run McAfee, so what they were thinking is beyond me)

I'm hoping someone here could maybe suggest something else I could try to fix this problem, and while I've pretty much reached the end of my knowledge base on this one, I'm a quick learner when pointed in the right direction!

Many thanks in advance for any help you can give!