I just hope the hard drive's not making the "Click Of Death"..

I wonder, would it be a good idea to just go into the boot menu (F8) and leave it running at that point? If it still restarts it's shouldn't be the hard drive or video card in that case.. (they're really not being massively used on a DOS-like menu) and if it doesn't restart, it's probably not overheating (assuming you leave it on for a while)