In Win2k memory is divided into pages. "Page fault in non paged area" translates approximately:
Something tried to write to an area of RAM it wasn't supposed to, the app/system tried to access memory in an area that isn't assigned to it, or the memory returned a bad/invalid value when it was queried. This is usually caused by bad/faulty memory or a bad driver. Win2k.sys is a system file so I wouldn't suspect it - unless you have a virus or haven't (re)updated to the latest SP after installing a new driver.
If you are overclocking this means you have gone a little too far - scale it back a notch and you should be OK.
I thought a thought, but the thought I thought wasn't the thought I thought I had thought.