Computer restarts when playing games

[XNinjaSheepX]

It all started one morning when I tried to turn on the computer and it just wouldn't turn on, no power at all inside. So I opened it up, dissconnected the cable going into the motherboard from the PSU and tried to start only the PSU by "hotwiring" the outputs according to a chart I found on the internet and the PSU didn't start, so I brought it in to the local computer shop and told them to do a hardware check and replace the PSU if it's faulty. A couple of hours later they called and said that it's the PSU and asking if they should order a new one, so I said yes and a couple of days later and -159€ from my wallet it was fixed.

This is when the real problems started, I plugged in the computer again and started it, everything started ok except two of the case fans where not spinning and the led lights where not on, other than that it seemed to be fine, so I tought it's probably nothing, they just forgot to plug them in, so I started up a game and then, about 5 mins into the game it restarted, no bluescreens, no errors on startup... I was totally confused and tried running a game again (BF3) and the same thing happened.

I called the shop, told the symptoms and brought it there, after a few weeks(!) it was done, no cost since I got it on their installation warranty they had. I got home, now the fans and leds are working but the same thing happened again, it restared without a warning. I searched the web and flicked through countless of forums and one day it was leaning towards a heating problem, the next day a driver problem, then maybe it's a HDD problem. There were a few Kernel Power ID
-41 (or something) in the windows logs. And now I also got a few bluescreens when turning off the computer stating that if I had recently installed new hardware I have to check them or something. I brought it back AGAIN and they reinstalled windows completely and said it works, and it did... for a couple of days, now the problem is back, happaned 30 mins ago.

What is going on? Could it be the PSU even tough it's only a few weeks old? I don't think it's overheating, GPU is around 70-78C on load and CPU is around 57-63C on load... Hard drive is 30C.

My specs:
Windows 7 Pro 64-bit
M4A77TD Pro ASUS motherboard
AMD Phenom II X4 955 Processor (3.2GHz)
NVidia GeForce GTX 260 Graphics card
6GB RAM
Nexus RX8500 850W PSU

Any help would be MUCH appreciated!

 

[clutchc]

My first impression (after ruling out the PSU) is that the motherboard is failing. Possibly a capacitor. Possibly one of many other components on the board.