Missing Process is using my CPU

[ravetroll]

I have a Athlon X2 4200 with XP installed. I have looked at process manager and I see the one processor is running flat out and the task manager graph says my system is running at approx 50%. Then when i look at the Process list it appears that System Idle Process is using around 99 to 95% of CPU time. There are no other processes listed using significant processing resources. So what is causing my one processor to run at full speed without being visible in Task manager?

 

[ravetroll]

I also sometimes run Vmware with Ubuntu Linux on it. This problem may be related to this since I think it has been happening since I started running ubuntu on vmware. Has anyone done this and had any problems?