If reformatting didn't help, its probably not software.

If is a video card, optical drive, floppy, cable, power supply or other gizmo you are good.

If its the proc. or the MB, you are probably screwed. You can't determine the problem without being an uber-nerd. I replaced a motherboard once to find out it was the proc. and I didn't want to spend $$$$ on an old board.

Good luck!!!