Motherboard or CPU dead?

[DCult]

I posted this in general hardware forum, but noone responded, so I hope someone will help here.

A weird story: I was playing HL2 Deathmatch the other day, and suddenly HL2-DM (as usual) crashed, but not in the usual way (datacache.dll).It froze, the sound went into endless loop and finally static came out of the speakers. Note that we have very hot weather in Greece these days and room temperature must have been over 33 degrees. I restarted the computer, it posted normaly, but instead of displaying the windows logo, the monitor received no signal and went to standby mode. I thought "that's a first, a game causes damage to the hardware". I immediately took the card (specs below) to the shop and they exchanged the card with a brand new one. I said "I got off pretty lightly". But when I installed the new card into the slot and powered on, the same thing. No windows logo, the computer boots normaly, I can blindly enter logon info and password and continues to work, just no signal to the monitor. I swapped the ATI1950Pro with a NVidia Geforce2 MX400 I had spare, and tada everything works normally, windows loads, but asks for driver and catalyst says that no ATI card is found (no **** sherlock). So what is it? Has the PSU gone bad (I have it more than 3 years) or is the AGP slot dead (the 3.3V)? Any ideas? Thanks in advance.

Some more info: Windows is not corrupt, every other subsystem works fine ( I had ms antivirus run for hours), windows setup dvd causes the same thing (when switching to vga mode after basic driver loading, monitors goes to stand by)

[Xion X2]

Are both cards AGP? Your original and the replacement that you tried?

If so, then I don't see how it could be that since the 2nd one worked. Do you have another PSU that you could swap in for testing?

[DCult]

Yes, the ATI is AGP8x, the nvidia is AGPx4. Anyway I ordered an Enermax Infiniti 650W, and brought a brand new spare ASUS i865G m/b that supports Core2 from the office, so I'll see how that goes.

[DCult]

Thanks for all the advice guys! I installed the 865 chipset M/B anyway and it had the same problem. Monitor losing signal, a little later though. (after typing the password). It was the PSU afterall. The new Enermax infinity 650W rocks. Well I guess the hassle was worth it since I am an owner of a E6600 now. Plus performance has nothing be jealous of DDR-2 systems, as I am running at 2-4-4 and getting better results in Sandra the equivalent E6600 DDR-2 systems there. And all of that without formatting the drive! Whoohoo!