I was using my computer the other day and walked away. While AFK it wen't into sleep mode and when I got back it wouldn't come out of sleep, so I powered it down. Since then it hasn't booted or anything. Just spins up (rather quietly compared to normal) and does nothing. No lights on the underside of my mouse/no lights come up on the keyboard. All the fans inside spin fine. Here's the specs as far as I can remember them;
Motherboard - ASRock Z68 Extreme3 Gen3
CPU - can't remember, but it is Intel
CPU heatsink - Cooler Master Hyper 212+
RAM - 2x sticks of G.SKILL Ripjaw 4gb DDR3-1600
PSU - Corsaid HX 750w
Video Card - EVGA GeForce GTX 560 Ti
HDD - Western Digital 1TB