Need major help, 6 month old problem

I own a custom built computer thats been givin gme the same issues for 6 months Ive tried everything to fix it the specs are

CPU-3.1ghz quad I5 INtel
16G of dual 1333 ram
azrock z68extreme 3 gen 3 mother board
nvidia 680 graphics card

at first everything ran fine i could battle field 3 at maxed out graphics, starcraft II as well, and the old republic. Then suddenly and ever since as im playing the screen will go black i can hear the music for 3 to 4 seconds then theirs a consistent low toned quickly repeating grinding sound coming from the speakers. when i start the computer back up it just says computer has recovered form an unexpected error. then it just says blue screen.

At first i though my graphics card was overheating i bought an arctic 3 graphics card cooler. That didn't work. I uninstalled and did a clean formatted install of all the drivers and the os as well. Still nothing, I can use itunes, surf the web. I can even play starcraft at dumbed down graphics but as soon as i even flip one thing up it does it to me again. Like i said i used to be able to play battle feild 3 maxed out now it wont last 1 minute running the game.

theirs no way its an over heat problem Ive even put a liquid cooler on the graphics card.

Please can any one help me out here, this is 6 months of a headache and an expensive one at that.