Help with no OS system

So I bought a laptop online that came without a OS. Unfortunately the computer will not stay on long enough to load any kind of OS on it (not even Ubuntu), I tried windows 7 and XP. The computer is an Asus G73JH-BST7. Now I'm fairly technical savvy. Here's what I tried as fixed (I got a little frustrated) -

Changed the memory

Changed the CPU

Flashed the most recent Bios

Loaded windows 7 on the hard drive from my desktop (to make sure the drive works fine)

Had a different Asus power supply as well as a universal one that I tried using

Tried running Ubuntu off the CD to get something (anything) done.

Changed Bios power settings, not that there really were any.

Changed bios to default.

And of course various combinations of playing with everything in the bios.

Anybody have any ideas? The only thing I haven't really checked is the graphics card (a radeon 5870m) but I really can't see how that could be the problem. As of now I'm chalking it up to a motherboard issue which I don't feel like dealing with so I'll be sending it back soon if no one has a fix.