Hiya, i've been experiencing the same problem recently.

check your RAM with Memtest. I did and found every module was 'bad' (i tested them one by one). This is interesting because i only upgraded to 8gb a short while ago and did a Memtest at the time, when it was fine. It's possible it's the motherboard, because it seems unlikely that all my RAM has died simultaneously - unless there was a spike or something. In my case, i suspect it's the mobo, which is of course the most annoying upgrade to have to make. The PSU seems fine (i have an inexpensive hardware PSU tester).

Man, i only just rebuilt (software), cleaned it out and upgraded to an SSD a short while ago (but before i did my earlier test - so something has happened since).