Gah, I should play Tribes more often. Every now and then I just get tired of being obliterated by people who have payed for bigger guns and quit for a while.
First off I think you should clear the CMOS, this will return all BIOS settings back to standard. There should be a jumper or button somewhere on the mobo where you can do this.
Check if that clears up the issue.
If it doesn't, I'l admit I am somewhat stumped. A PSU or HDD failure wouldn't cause the issues described. Bad memory might though, run memtest to find out if its a problem.
Guess all you can do is run it breadboarded, so oustide the case on a non-conductive surface (wooden table, plastic mat, cardboard are all good surfaces). Remove everything that isn't required to boot the machine (only one RAM stick). If it fails, swap the stick. If it works, you know that sticks at fault. If it still fails, it can mean both sticks are bad, but you cant be sure. If it all works, keep adding components on until it fails. That will get you a general idea of what is causing the issue, and whether the problem is hardware or software based.