Computer Restarts while playing games, no idea why

I agree, if the machine is restarting randomly, the power supply is always the first thing I would check. It's pretty hard to overload a 1000W PSU with a single card, though, so it would have to be a defect, not overloading. The PSU could also be overheating if its fan is jammed.

The simplest way to check for PSU problems is usually to find another one they you can borrow from another machine and see if the system stabilizes. If that's not an option, they also have free programs like CPUID's PC Wizard that can monitor the output on each of your rails. If the voltage is too far from spec on any of them (e.g. the 12V rail is below 11.4V or above 12.6V), then that indicates a likely problem with the PSU itself.

If the restarting is happening at a specific point in the same games, that could also indicate a bad sector in your RAM -- at that specific point, something in the game calls on the bad sector, and poof! no more game. Usually it's more common with RAM issues to get a crash/BSOD though, not a reboot.

What are you doing with 12GB of RAM, by the way? Please tell me something to do with graphic design.

Sadly this is the only power supply i have, so i cant switch it out to test a different one
i cleaned out the psu, took out all the dust and stuff i could get without taking it apart, and it still didn't fix it. though i noticed something, the computer restarts more frequently during the day, then at night,
if that means anything.
im pretty sure its not the game, or specific point in the games
cause i could be doing anything (in the game) and BOOM restart out of no where.
and it never BSOD's (i kind of wish it did, maybe I'd be able to fix this lol)

oh lol the 12gb's is from when i was doing video editing, and i saw a pack of 3x2GB's on sale so i picked them up

thank you for the response  

That would seem to indicate a thermal problem.

I would have thought it was the GPU. I had a similar problem a while ago, where my Radeon 4850 would hit temperatures of up to 120C during games.

I've heard of similar problems being caused by faulty PSUs, but those have usually been cheap ones, not high end PSUs made by a reputable manufacturer like Antec.