BleepingComputer.com: trouble with AGP video cards

Hi,

I went through two AGP video cards, and experienced the same symptoms on both. The first was a 7900GS. The fan stopped spinning. Sometimes it would spin, sometimes it would start then stop. Anyway, the card died, I assume because the GPU was running at 110C+.

Just to be sure, I took out the PSU and tested it in a different computer. Everything worked fine (that computer also had an AGP card, but it had no connector for PSU cable, just went straight to mobo AGP slot). So, since I thought I eliminated the PSU, I replaced the 7900GS with a Sapphire 9600xt (256mb). This card has no PSU connector, and just plugs straight into AGP slot.

Everything worked fine, initially. After 30 minutes or so, the fan started making a strange noise. Now, this is the second card where the first symptom is the fan. I thought I ruled out the PSU, but this is giving me doubts. What is the most likely cause? Motherboard? PSU? AGP slot?

I'd appreciate any help.

My system:

P4 2.4c, 512MB ram, ASUS P4P800SE, running Win XP (SP2)