HP 6120 Laptop Randomly Shutting Off

Hello,

I have an HP nc610 laptop from my company that is randomly shutting off. The bad thing is that it does not record ANYTHING in the Event Logs -- nothing in System, App, or Security. There is no blue screen of death nor any error when the PC boots back up. It just simply shuts off seemingly at random intervals.

My diagnostic testing thus far has covered the following: I have run a memory test from within the PC's BIOS.  Interestingly enough, the PC shut off several times before I could actually  get it to stay in BIOS long enough to run the memory test. Once it started testing, it got to 100% but then almost immediately shut off.  What's even more interesting though is that the PC reportedly passed all 4 memory test results. I have also run a chkdsk /r and it found and repaired errors accordingly.  I downloaded a free temperature gauging software and my CPU temp is a steady 55C as I type this. Sys and Aux temps show 52C, while the HD shows 32C.

The system itself has 2GB of memory but as stated it passed the BIOS test. I have tried to do a Repair Installation but I cannot get the PC to boot to the CD long enough without shutting down. Once I got as far as the first setup screen, but then it shut off as usual. It seems to allow me to do work (such as type this desperate plea) for quite a while, but I am fearful it will shut down before I get a chance to submit this lengthy topic.

The PC is also equipped with Sophos Anti-Virus which is updated and no viruses found. I have run msconfig to remove any unnecessary or unknown programs from startup and also thoroughly checked for spyware with programs such as HiJackThis.

With that said, it seems like it's definitely a hardware problem because the PC will shut off if I am doing something that doesn't even involve booting the OS (such as booting to the CD Drive) -- so, what could it be? Failing CPU? Failing...mobo? Inadequate PSU? (FYI, yes, the PC reboots regardless if it's using it's fully working battery or AC power) Are that any programs or utilities that could test for those failing devices? I only ask this because unfortunately I don't have spare parts that are compatible with this model that I could use for testing.

Any help on this would be greatly appreciated. I realize it may be tough to troubleshoot something like this, so hopefully you can understand my own predicament, however I am confident the talented EE community will pull through as usual :)

Btw, I am offering the only points I have available, otherwise I would make it worth much more. Sorry!

Thank you.