Does it have a warranty? check if you can return it, it might be a hardware issue, have you done anything recently that could cause this? sometimes this will happen to computers that have bad hardware when being made (Example i bought an MSI Wind net-book and the first time i turned it on it froze, i restarted it and couldn't start assuming it was a hardware issue returned it and got an ACER ASPIRE 5517 and had no problems)
"Just like a Hard-drive, the computer will ether die at the beginning of its lifespan or at the end, anything else in between may be caused by the user or a program"
