Random Reboot with Intel DP43TF

[wprivera]

OS: Windows 7 Ultimate 32 Bit
MB: Intel DP43TF
CPU: Intel Q8300
RAM: Corsair Dominator 800 Mhz
CPU: 550 Watt
Video: ATI HD 5770

I recently built an HTPC with the Intel DP43TF Motherboard with a Q8300 CPU and 4GB of Corsair Dominator Memory. The board runs fine with a video card that does not require an additional power source. But when I use an ATI HD 4370, and later an ATI HD 5770, the computer randomly reboots. The 550 watt power supply has a 6 pin molex for the video card.

Strange, I know. The case has 5 fans, and I do not have any heat, or power issues, as the system monitor software does not identify any. Incidentally, the Chasis Outlet Fan Header does not supply power to any fan when connected. I tried several.

I've upgraded the BIOS, Chipset and Video drivers to the latest releases. I've run Memory and CPU diagnostics. No errors are identified. I feel I have a bad motherboard and think I should RMA it. Any thoughts...

 

[wprivera]

The PSU is a Generic $48 one from Fry's. What do you suggest?

 

[wprivera]

I've had difficulty with power supplies on other builds, so your logic of replacing the PSU sounded reasonable to me. I drove down to Fry's and picked up a CoolerMaster Extreme Power Plus 700W (RS-700-PCAA-E3). When I opened my case, I was surprised to find that I had previously purchased a CoolerMaster Power Supply 500W (RS-500-PCAR-A3). I switched them out anyway.

Now, I'll do some intensive video watching and see what happens. The Rear Chasis Outlet Fan now works, but sporadically. I have 5 new CoolerMaster 80mm fans.
Any further thoughts on the quirkyness of the fan operation>