Firstly - sorry for the long post, but if i just say it all now then there wont be any time wasted or asking for more info later.
During normal operation, my system runs quickly and smoothly. When playing Team Fortress 2 it still runs smoothly and I can play for hours with no interruptions - hardly surprising as it's not exactly graphics intensive. BUT the moment I try and play a more 'serious' game, after approx 5-10 minutes, the screen goes black then 5 or so seconds later the PC reboots. I have tried everything to investigate this and fix it and I'm all out of ideas.
The games I've tried are Crysis3 and Deus Ex. I've installed the Nvidia GeForce Experience and the latest drivers, I've even dropped the settings to a lot lower than the 'optimum' it recommends, yet it still crashes. The strange thing is, its never at the same points, never after a set time.
I have a watercooled system, looking at the temps using Realtemp GT (I know its only CPU - not sure how this relates to the water temp or GPU temps - if anyone has a good GPU temp reader then please let me know!) and they're never more than 75 degrees even running prime 95 - rarely get above 70 during gameplay (even on higher settings).
I have a GTX 680 Hydrocopper GPU (Driver 331.82), i7-3770K (stock), 16 Gb Corsair Vengeance RAM and screen res is only 1080p.
I have tried every method of fixing it I could find, including:
Run a graphic stress test like FurMark or OCCT
Install the latest Nvidia drivers, no need to install GeForce Experience, and enable clean install
If it's possible, try the graphic card in another slot. Watch out with your tubing
Try a different power supply
I only installed the Geforce Experience so to get an idea of settings I 'should'(/could) use and to check the drivers were up to dat quickly and easily.
I didn't know of any GPU stress tests, after 10 minutes running furmark my GPU temp hit 101 degrees. Whilst that is excessively hot, when playing crysis3 or deus Ex the GPU temp stayed much lower ~70 degrees