Motherboard Problems?

So, working on girlfriend's parents computer and running into a problem. Not sure what happened, be it a virus, something they did, or an act of fate, the computer keeps freezing at the POST screen. Starting up the computer everything seems to be fine (except the power supply making a high pitched scream like an old CRT monitor), however it has been doing that for a while) the first thing i notice is the RAM speed display, where it used to display the total RAM inserted (512MB) all it says is 333, not 333MB just 333, does that mean the computer is possessed by a half demon? I'm not sure, moving on. After it completes POST I have gone 2 separate directions: 1) the computer allows me to the "windows did not shut down properly" screen seemingly about to boot up, however no matter what mode i choose (normally, safe mode, etc) the computer freezes, and I have even let it sit at that screen for a couple seconds but before the timer can even reach 26 its frozen 2) attempting to enter BIOS, Boot Options, or System screens causes either immediate crash or takes me to a hardware diagnostics screen where all it loads is the CPU temp (Pentium 4 running at 2.6GHz, 76 degrees C) before it crashes. I have removed all unnecessary components including video card, NIC, and sound card, run it with both 256 sticks of DDR ram, one 256 stick (tried one then the other in either slot), as well as a known good stick of 256 salvaged from one of my old comps. I have even tried booting without RAM or Hard Drive, and the computer doesn't even give me a beep code before it freezes. At this point I have also kind of shot myself in the foot because I re-set the BIOS hoping to solve something, but now it freezes before i can reconfigure the BIOS. I know I don't exactly have a PHD in computer hardware but I like to think I know my stuff at least a little bit. Is there something I am missing? Any help would be appreciated.