Sounds like a hardware failure. Possilbly the motherboard, more than likely, the power supply.
But then - maybe neither.
Shut it off completely, once you restart, start hitting the F8 key ( once a second ) until you see the " Safe Mode" choices screen. Drop down and select the " Last known Good Configuration" option and hit enter.
If this doesnt work, try the same proceedures ( restart - F8 ) but this time select safe mode - at the top of the list.
If you sucessfully boot in safe mode, you have a system file problem that could be virus related, file table corruptions or registry problems or all combined.
We're here if you need us.
www.wvpcrepair.com