rebooting PC

Usually reboots are due to bad Power supplies. How big and what brand is your power supply? I suggest testing the rails to ensure proper +5 +12 and -5 and -12. How old is the system? Any of the above new hardware since the problem emerged? I forget where but I think in the MMC there is a spot that you can turn off reboot if problem happens, but I cant remember where or what the exact wording is. I dont like the kernel error though. I take it your running NT?

Power Supply or Heat Problem.

I Tshooted a couple systems that would shut down after 3/4 hours of operations. Then I saw the power supply fan not moving or the actual MoBo caked in dust just cooking itself to a slow death. There's a couple freeware programs out on the net that takes your system's temps, try them

if you've gotten the blue screen, that means it's a windows issue not hardware. you will need to elaborate a lot more plus run a gauntlet of system tests.
generally ntoskrnl errors on blue screens which are coupled with involuntary reboots require immediate virus scans.
it is the core kernel (or deployment workhorse) which initially loads win2k and then calls upon the remainder of the GUI boot process, while continuing to run in the background to support win explorer and app launches.
this is simply the definition.
now what to check for is in the event viewer in admin tools.
sounds like your hardware is quite adequate.
in event viewer you'll see the red x and the time the error occured. this will give you some insight into what happened. you could have a virus, a program you aren't aware may not be compatible with 2k or just a corrupt windows system (general term i know, but then again, this is microsoft we're talking about)
if you can elaborate more on events leading up to the reboot or blue screen, i can help you further.
-Orpheum