So your saying that when you turn the computer on and it shows the black screen with how much ram you have etc etc it just freezes?. Hmm sounds like you flashed it or somthing with the hardware is just overheatin or stoping. If I where you check the ram in a other computer, maby the cpu if possable.. Past that im out of Ideas.. Maby someone in this forum can help to!
EDIT You can always put the harddrive in a other computer that your using right now and back the information right there.!