Odd Reboot When Logging in or not Gaming

I have been having this problem for about 2 months now, and I am very, very stressed over it.
My build is as listed.
Basically, my computer runs very well with the exception that it randomly reboots (or, at least I think it is rebooting).
The video goes but the sound remains, and at the same time the fan on my video card gets louder. It stays like this for a while before giving up on sound, and eventually I must turn it off or restart it on my own (by using the buttons on the case).
This has never happened in safe mode.
All of the parts are new.
This never happens when I am playing a game, but does happen while loading games.
So, after consulting a large amount of customer support representatives, I have concluded the following:

1) It is not a virus. I reinstalled Windows 7 (twice) and the problem remains.
2) It is not (I think) a driver problem. All of my drivers are up to date.
3) It is not my PSU. I contacted the company and was told that because all of my voltages are reading correctly that it should be fine.
4) Nothing is overheating. I have used various temperature monitors and everything is reading well below any critical levels.
5) It is not a RAM issue. I did all of the tests I could and Windows recognizes all 4GB, the mobo has the correct timings for the RAM.
6) It is not the hard drive. I ran a recommended test and everything is fine.
7) It is not the CPU. Originally my CPU was overheating, but that was a bad part. I RMA'd it and bought a new heatsink, so it should be fine.
8) It is not the video card. I sent the video card back as a last resort, at which time the company checked it out for me. It is running fine.
9) It is not the monitor. The monitor runs fine with my netbook.

I have no idea if, maybe while my original CPU was installed and overheating, a capacitor or something on my motherboard broke. I also have no idea if it is a compatibility issue between my monitor and VGA, but I just doubt it.
Also, I have enough power.

Does anyone have any ideas? I have actually cried over this. It is very disappointing that something I invested so much in should have these issues. I just want something nice, for once, that works.

Thank you for any help.

John

have you checked your voltage settings in your bios? check your ram and cpu voltage. also if you are still overclocked you may want to boost the north bridge voltage up aswell.
hope this helps

scrooge

Scrooge, I checked those values when I checked my PSU. They are fine.
Richc46, I'll try that now.

Thank you you two.

I just went through of the clean boot procedure, and came up empty handed. I guess that the drivers aren't my problem. If it's hardware then I guess it might be my mobo....I guess.
I found that when I leave the computer off and unplugged for a while then it seems to restart less often. However, the longer it is plugged in the more often it restarts. (Again, not a heat issue).