Also check your powersupply its the most common hardware for a computer to crap out on ya =) Most powersupplys have a 100,000 hour limit before they are prone to die on you check out how old your powersupply is

well that could be the problem then. get your electricity checked out then. maybe try taking some stuff off of the circuit your pc is on.
Ive had the same problem, you need to take out your RAM and start it, then turn off, then you put your RAM in again. It should work, did for me.