Intermittent Video Lockups After 5mins

[MunchE]

Problem description: When I load up a 3D game, everything works fine. After about 5 minutes, my framerate will drop to like, .3FPS and the game becomes a slideshow for 30-60 seconds. It then returns immediately to normal and my framerate will go back up to the high framerate it was before. The problem then happens every 60-90 seconds. Pretty much renders games unplayable. This started happening a month ago in AoC and I thought it was an AoC problem, but I tested it in TF2 and it's happening there as well. This system worked fine for ~6 months before thise.
Attempted fixes: Updated/Reinstalled Video drivers, nForce drivers
Updated motherboard bios
Replaced 8600GT with an 8800GTS (No change better or worse...well I get a better framerate between lockups)
Recent changes: No hardware or major software changes before this
Operating system: Windows XP Pro
System specs: let's just copy from my invoice
Intel Core 2 Duo E6550
G.SKILL 2GB (2 x 1GB) 240-Pin DDR2 SDRAM
Western Digital Caviar 320GB 7200 RPM SATA
MSI P6N SLI-FI LGA 775 NVIDIA nForce 650i SLI ATX Intel Motherboard
Rosewill 400W ATX12V V2.2 PSU <- #1 suspect. The only thing that throws me off is, the problem didn't get any better or worse with the new power hungry card, or when I unhook my 2 external hard drives
EVGA GeForce 8600GT 256MB, now upgraded to an BFGTech 8800GTS 512

Here's my DXDIAG: http://www.iz-us.com/DxDiag.txt

 

[Dangman]

Disable any anti-virus or firewall app running in the background. In fact disable any unnecessary program running in the background that won't affect the stability of the PC.

Also, clean out your case. It might be an overheating problem.

 

[MunchE]

Disable any anti-virus or firewall app running in the background. In fact disable any unnecessary program running in the background that won't affect the stability of the PC.

Also, clean out your case. It might be an overheating problem.

Heat hadn't occured to me....checked a temperature monitor, sure enough, my CPU was hitting 80C at the lockups

Opened the case, tons of dust on the CPU fan. Cleaned it out....now we're sitting at 55C with no more lockups.

Thanks!

 

[Dangman]

You're welcome!