Motherboard problem or PSU not sure

My brother built this computer, its been working Godly since he build it which was in August 2010. Randomly, while playing Starcraft II, the computer randomly shuts off, powers on for like 4 seconds and shuts off again. What can this be? And ever since the shut off, the computer will not boot at all, the mobo LED is lit green and the razor mouse that we have is also on even if the computer is shut off. The computer does turn on but the CPU fan and the GPU fan do not seem to be working, only the shell case fans and the LED lights around the case work. There are no beeps when you turn on the computer as well, and the monitor is on standby as the computer is not booting up. We looked around the internet, tried re-fitting the RAM, Still no luck  


I don't really know much about specs of the computer but grabbing the boxes i'll list down each part used in the computer
TX850W power supply, corsair
M4N75TD Asus motherboard
Asus ENGTx460 DirectCU GeForce GTx460
AMD Phenom II black edition multi-core processor
Corsair XMS3 2 x 2GB DDR3
All i know is, its a 1 TB harddrive and an Intel x25-v sata solid state drive 40gb

Much help would be appreciated, thank you!