Well man, how the can it be my PSU? it's brand new, bought it today for this build. I can't be too weak, the 600w does the exact same thing. And the one I had before I bought that one did the same, too and it wasnt a Thermaltake
Here's some quotes from the review of the Purepower 430:
"The conclusion is that according to our methodology Thermaltake Purepower 430 W NP isn’t a 430 W power supply, but a 350 W model! We also could only pull 16 A from its +12 V output, while the label says the limit is 18 A."
"Our conclusion is pretty simple: don’t buy this power supply."
It doesn't sound like you've used a decent PSU in this system yet. The 9800GT needs more power than this PSU can produce.
Another thing to check is the RAM settings. What exact model of RAM do you have? Did you manually set the RAM speed/timings/voltage to the manufacturers specs in the BIOS? Have you run memtest86+ overnight to test for RAM errors?
Well, if the 600W PSU was a Thermaltake Purepower PSU it was probably a POS also. It was probably more like a low-end 450W - 500W PSU. Thermaltake likes to give their PSU's a rating that's higher than they can acually produce. You really need to look for a quality PSU from Corsair, PC Power & Cooling, Seasonic, Antec, etc... Going from one POS to another doesn't eliminate the PSU as the problem.
Alright. But let me tell you something. This build was running fine on my other computer, with the 600w PSU. Never had any shutdown problem at all. Only thing I switched was the case, HDDs and DVD Drives. I'm not trying to prove you wrong, I know you're right, but you have to admit this is really ****ed up in itself, isnt it?
--sorry the kinda bad words filter filtered out my whole post.