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Windows XP, SP3, Intel Core 2 Duo

Here are the symptoms:

  • Since a couple of days is my System task permanently at about 35%
  • When I want to Turn Off the computer then the Explorer needs to be force quit (not responding).
  • One core is always at 100%, the other is always at about 30%
  • Top busy tasks in the Task Manager: System 35%, System Idle Process 50%, Explorer 5%
  • Nothing strange is showing up with ProcessExplorer, which would explain the CPU usage.
  • Firewall is on.
  • I don't have any AntiVirus Software installed (it's not connected to the internet ever anyway)

The computer is NEVER connected to the internet in any which way (and also not connected to my LAN because I have a massive paranoia in terms of Windows). I did not install anything in the last months. I only use the PC to develop some software (VS 2010).

How can I find out what's going on? Why do I need to force quit the Explorer when I shut it down? Something is probably "stuck" there and clogs the CPU...

Edit: Disabling the Startup items with MSCONFIG.EXE does not help. Even with everything disabled the System task is still at 35%.

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migrated from Jun 2 '11 at 19:09

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Have you tried a system restore? – soandos Jun 2 '11 at 19:27
Are you viewing processes by all users in task manager? (I think process explorer does this already, but you MIGHT have to run it as admin to see all users) – horatio Jun 2 '11 at 19:27
Start by seeing if this happens in safe mode as well. If it does, then I would like at software that is loading and what drivers are loading on safe startup. Im willing to bet its probably a badly written driver, that doesnt show up and is causing this issue. do a windows verification test on the drivers to see which arent signed. – francisswest Jun 2 '11 at 19:31
I did not use system restore ever. I am viewing processes by all users. There is only one user registered anyway, and yes, it is an admin account. – Christoph Jun 2 '11 at 19:31
@Christoph "Once you eliminate the impossible whatever remains, no matter how improbable, must be the truth." Sounds like a virus to me. Do you use any USB drives, CD-ROMs...floppies even for backup? I have personally bought brand new discs that come with viruses pre-installed. – P.Brian.Mackey Jun 2 '11 at 19:42

Run MSCONFIG.EXE to examine the programs that start up when your system is booted. Disable all startup items, reboot, and see if your system still has high CPU utilization. Assuming everything is back to normal, starting adding the startup items back in one at a time, rebooting after each change, until you have identified the program that is the culprit. I've had good luck tracking down programs that cause high CPU utilization with this troubleshooting method, but it does take some patience.

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This is a good general approach, but can take a long time - a quicker variation, is to disable half of the items. If all OK, then disable the other half and reenable the first half. Repeat with the halving until can isolate the problem. It should only take a small number of reboots. – barryj Jun 2 '11 at 21:37
I've tested it and deactivated all startup items. The problem still persists with everything disabled. – Christoph Jun 3 '11 at 5:29

Top busy tasks in the Task Manager: System 35%, System Idle Process 50%, Explorer 5%

This means the problem lies with something in the System, this could most likely be due to drivers.

Nothing strange is showing up with Process Explorer, which would explain the CPU usage.

Have you checked the threads tab under the System process?

Also, you could try this procedure which allows us to see in detail what the System process is doing? It would turn all the guess work and irrelevant solutions into knowing exactly where the problem lies...

As your problem is always happening rather than on event, you might as well get a faster answer by trying out LatencyMon and looking in the Drivers tab at the processes that have an abnormal DPC count or highest execution time. Either one of these will cause high CPU in the System process, unless it was something in the kernel which I highly doubt but is still possible...

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Sounds like Malware to me, see my post in this thread to remove malware

What to do if my computer is infected by a virus or a malware?

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First, install the latest driver software for the hardware you have on your computer. Once in a while a driver will screw up and drive up the CPU time.

If that does not help, do a backup and reinstall windows. I have been repairing computers for two decades and strongly recommend against after-the-fact virus removal.

Not only does it rarely work, but you never know if you really got rid of the virus or just stopped some of the more obvious systems while leaving..whoops...the keylogger/emailer functions. See Microsoft MVP Robear Dyer's answer to this as well.

System restore also cannot be depended upon for virus removal. The restoration files sit on the same system as the infected machine and since you are logged in as administrator then any potential viruses will simply run as you ensuring full admin rights to destroy the backup.

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Since you say that it is never connected to the Internet, we can all but rule out viruses, so you almost certainly have almost certainly corrupted some important program file along the way.

  1. Start by opening a command prompt and run the command: sfc /scannnow . That will check to make sure that all your important Windows files are correct and intact.
  2. See if it does it in Safe Mode. If that does not do it, you will need to figure out what process is killing you. Open msconfig.exe and go to the startup tab. Uncheck or disable them all. Then see if that fixes it. Re-enable them one, or a few at a time until you find the one that is causing the problems. Repair or reinstall the program associated with that startup item.
  3. If none of this works, there are other ways you could have infected yourself, so just in case, run both Malwarebytes and Superantispyware.
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1. Tried it. Does not like my CD. Gotta find the one I was using to install XP. 2. No CPU hogging in Safe Mode. 3.I've ran both (Malwarebytes and Superantispyware) and they both found nothing. – Christoph Jun 3 '11 at 5:26

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