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I'm experiencing a problem where XP freezes completely for a fraction of a second, every second. The mouse doesn't update, music stops, video stops - and then suddenly resumes.

I can't see anything using any CPU in Task Manager, and I've tried shutting down every service I can identify. There's nothing obvious in the Event Viewer.

The CPU graph (at highest refresh rate) looks like this for one of the two CPUs:

enter image description here

The "CPU Usage" alternates between showing 2% and 25% (ie, one CPU 50% utilised).

There is no significant network traffic. I can't think of anything else that could be causing it. Ideas?

UPDATE The next day, it wasn't doing this. But by the end of the day (after several hours sitting idle) it had reappeared. So apparently related to the machine being on for a while.

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How about RAM usage? In Task Manager, look under the Performance tab at 'Physical Memory'. How much as available? – TheTurkey Feb 12 '13 at 12:06
What does the task manager say is using the CPU? – David Schwartz Feb 12 '13 at 12:36
Have you scanned for viruses and malware/spyware? Does it do the same thing in all user profiles or Safe Mode? – CharlieRB Feb 12 '13 at 12:54
Are you running Skype? – Dave M Feb 12 '13 at 13:14
Try checking for updates (Windows and any extra software), maybe it's a bug that has been fixed meanwhile. – vonbrand Feb 12 '13 at 13:28

Lately I'd the same problem with my PC, and it turned out that CPU fan is not working.
If the temperature of CPU gets higher, it can make CPU work slower.

Use tools such as AIDA64 to know temperature of your processor.
Or open the case of your PC and look if your fan is working normally.

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Great idea. I use SpeedFan - yes, most sensors are running hot. However, I've now tried putting a huge fan next to the PC (cooling it back to normal range) - still doing it. – Steve Bennett Feb 15 '13 at 8:20

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