I'll try to be very specific with what is happening, after writing down my system specs.
I have an ASUS M5A97 R2.0, installed all the drivers from the CD that it came with and the BIOS version is only a few months old.
8 Gigs of RAM, system reads all 8 as usable.
GeForce 9800 GTX+ Video Card.
700 Watt Power Supply.
A 250+ Gig Hard drive.
No CD drives currently.
AMD FX-4170 Quad-Core Processor 4.20 GHz
64-bit operating system.
Windows boots up fine, I load up a game, Shogun 2 Total War, and the computer will power down once it gets to the menu screen, which involves a 3D background usually consisting of buildings or a ship with a slowly panning camera. (I have managed to get into the game one time and actually start playing the game, a whole battle, even, before it shut down immediately afterwards) When I say power down, I mean it is as though someone pulled the plug on it. Then, when I try to boot it up, it refuses to power back on until I turn the switch on the back of the power supply off then on. At this point, it will power down in a similar fashion while in the middle of loading up my desktop, after I've input my password and everything. I've done a HeavyLoad stress test and it does not recreate the issue, and it stresses it to 100% CPU use, supposedly tests RAM, etc.
I've tried removing one of my RAM sticks, having two 4 gig sticks, same result. Another thing is that it gives me CPU Fan Error! upon booting up. I disabled the monitoring on all the fans to get rid of this in BIOS setup. The fan on the processor seems to be running just fine.. I'm watching it through the open case of my computer. Keep in mind also that the room is chilled, like.. you have to wrap up in a blanket just to sit in here chilled.
Speedfan is telling me that my GPU stays between 39-45 C, 45 being when I am running HeavyLoad.
After wrestling with it a bit, it will eventually load windows again, i'm not sure if it is overheating issues.. Would the stock cooling unit on the processor not be enough? For the processor itself, anyway.
Someone suggested that it might not need to overheat to want to shut down due to overheating issues, not sensing a fan during high CPU usage causing it to simply shut down in a preemptive attempt to prevent overheating. Though this does not explain why things seem just fine when HeavyLoad bogs down my PC with stress tests.
I woke up this morning and booted the computer up. Ran Shogun 2. Didn't crash.. played the game just fine. Didn't play for terribly long, but the video card did heat up to about 54 C. I shut down the computer, brought up BIOs and checked the processor temperature and it was perfectly fine. So while symptoms point to overheating, nothing seems to be very hot save for the video card, and that's kind of normal from what I understand.