I would be looking at the CPU and CPU fan first, then case fans. Assuming you set up CPU/grease etc. Could be that the supply is whimpy but tend to lean toward heating issues created by component cooling.
I recently bought a XION 630 watt atx power supply that was both Intel and Nvidia ready, assuming that it would sufficiently replace the default 300 watt power supply that came with my computer. Basically, I needed to power a Geforce gtx 465 card that I had installed on my computer. It worked well for a while, but crashed shortly after playing a demanding game and overheating.
The cooling fan is located on the bottom of the power supply, and I don't think there is enough airflow.
Windows 7 64 bit
Intel Core i7 860
8GB DDR3 RAM
1TB hard drive
Geforce Gtx 465