I've been having some trouble with high CPU usage from my system process intermittently for quite a while (months). More recently, it is present all the time that Windows is running. Running with procexp sampling twice per second, the System process seems to oscillate between 0% and ~40% (ie, most of one core) with a period of two seconds.
I'm running Vista Business 32bit and Norton Internet Security. After posting on sysinternals forum, I've now uninstalled Norton in case that could might help, but it made no difference. I can of course provide other details of my system that might be useful.
I think I've done about as much diagnosis as I can at this point without asking for more expert advice. With procexp, I could see that ntkrnlpa was implicated, and following instructions here http://rfvicente.spaces.live.com/blog/cns!5228FAA8B79B6EB1!590.entry I got kernrate to tell me that KiDispatchInterrupt constitutes 84% of hits within that module.
So now what? What can I discern from these facts? It seems like it might be driver related, but I don't know what driver it is likely to be, and I'd rather just reinstall Windows than spend ridiculously long diagnosing the problem.
If anyone has a suggestion of what kind of drivers or other things might cause this, it would be much appreciated.