Desktop Hardware and Upgrade Questions

Ok. Trying to fix a friend's computer, and seem to have run into a rather strange snag. 

Problem:  The computer will not boot past the bios screen. 

Details:  When you power on the computer, the compaq logo with intel inside shows up and has the <F1 Setup> and <F10 System Recovery> options listed as well.  And this is about as far as the computer gets.  After this the whole computer is just locked up, no buttons work on the keyboard no lights come on the keyboard ect ect.  I've tried mashing on the F1 key as soon as I power on the computer and I can manage to get it to say *entering setup* but it still freezes after this point.  I've already tried eliminating possible sources of problem, all expansion cards removed, HDD and Dvd Rom disconnected, single memory module (256mb ddr 2700), only power, vga, and keyboard connected.  Ive also used the jumper on the motherboard to clear the cmos hoping that would solve the problem, to no avail.  I've tried using a different stick of memory and different memory slot as well...  Tried using both a ps2 and a usb keyboard... Ive even tried pulling out the jumper for the bios password protection (even though it didn't have a password on it, just trying anything I can think of). 

The installed bios version is 3.1, and that is about all I know about the computer at this point, other than what the website tells me of it. 

 http://h10025.www1.hp.com/ewfrf/wc/product?product=411354&lc=en&cc=us&dlc=en&submit.y=5&submit.x=3&lang=en&cc=us <-- link to the webpage for the model #.

I am basically at a loss on this one, so if anyone feels up to racking their brain on this one, I would greatly appreciate it.  

I've got a pretty strong knowledge of computer repair, so feel free to give me anything to try.  

If you need anymore info out of me, let me know as well.