CPU usage jumps to 100% -> WHEN <- machine is idle (not the idle process) [duplicate]

Possible Duplicate:
Task Manager shows 100% CPU utilization, but nothing in process list does.

My friend has a machine in his teashop that I am attempting to troubleshoot, so far with minimal success. It is a WinXP, 500MB, 2.12GHz. Nothing spectacular by today's standards, but a reasonable piece of equipment.

In the last couple of months, it has started a behavior that I have so far been unable to repair. When the machine sits idle for a while, it suddenly jumps to 100% CPU usage for no apparent reason. It has WinAmp running almost constantly, playing background music in the teashop, and usually a browser open, which the owner plods around on the net when not busy with the shop. This all works well and when WinAmp is running, usage is around 3-5%, as one might expect.

But when the owner leaves the computer idle for some time, the usage suddenly jumps to 100%, to the point where WinAmp can't even keep up - the played sound stutters so badly it's unrecognizable as music. This continues for around ten seconds, then stops, then resumes fifteen to twenty seconds later, stops again, and so on. It only quits when someone moves the mouse or presses a key. This happens regardless of whether a browser is open or not, and I've tried all three of the biggies.

The process names window shows nothing using that much power, although the CPU utilization line is at 100%. And it's almost impossible to do any research into the problem, because as soon as I move the mouse, it stops. I have an anti-virus (NOD32), have checked for spyware, unloaded everything suspicious from the start-up configs and installed a load balancing tool called ProcTamer. Nothing has helped.

Can anyone suggest something to try?

Solution 1:

One way to diagnose this might be to open the task manager pre-emptively.

Switch to the "Processes" tab and enable the "Show processes from all users" option. Then sort the grid by CPU - a single click on the heading of the CPU column should do this (click again if System Idle Process isn't at the top).

Then when the problem starts you should be able to look at this view and see what's now at the top of the grid. Make a note of the process name then search using Google or ask another question for more information.

Solution 2:

I would suggest delving deeper into the process list using Microsoft's ProcessExplorer. It will show you all the resources all the processes are using, and even make you some nice graphs to look at. It should pinpoint the process that's doing the dirty on you.