Well, does it boot through BIOS then kill out, or does it just flicker on then kill, repeat? If your BIOS is showing on the screen, I'd put my money on your HDD (especially since anything over 50 G's will do it in pretty good). Depending on your location, I would remove the HDD and take it to a tech store and see if they can mount the HDD and verify it's functionality, unless you have the cables and knowhow to do it yourself.