Windows 8 100% CPU use idle by disk degragmenter

Of the four computers I installed Windows 8 Professional upgrade to, one of the computers will jump to 99-100% CPU use when idle for about a minute. Any activity by me (access menus or programs) results in the Service Host: Disk Defragmenter to stop and return to normal low CPU use. The PC has three hard drives, all of which report to be fully defragged (ought to be after days of defragging ;-) ).


I unplugged two of the hard drives to determine if one drive might be the culprit, but no change was observed.


The CPU temperature jumps from about 42 degrees Celcius to 49 degrees while the task manager is showing the defragmenter to be running, so I am assuming that the CPU graph in task manager is correctly showing CPU activity.


While the disk defragmenter is running there is 0% disk activity on the graph as well as the hard drive indicator light showing no activity.


The computer is also often very slow to boot, sometimes taking ten to fifteen minutes or longer (I do not use the computer very often so I thought that perhaps it was installing updates).


The computer is a home-grown Asus M3A motherboard, AMD Sempron LE-1300, and 4g RAM. Windows 8 was installed over the existing XP.


Before I attempt a reinstallation (eek! lots of programs!) I was hoping that someone might know of a quick fix. Thanks!


Hi Larry,


Thank you for posting your query in Microsoft community forums.


I understand the issues that you are facing in Windows 8 computer.


I would suggest you to perform the methods given below and check if the issue persists.


For issue With 100% CPU usage.


Method 1: Try booting the system in safe mode and perform a clean boot.


Step 1: Perform Safe Mode


Click the link and follow the steps “Windows Startup Settings (including safe mode)


Check if you face the same issue in safe mode. If the issue doesn’t persists in safe mode, the place the computer in clean boot and check.


Step 2: Perform Clean Boot.


To help troubleshoot error messages and other issues, you can start Windows 8 by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts.


Important: Reset the computer to start as usual.


Note: After you have finished troubleshooting, follow these steps to boot to normal startup.


a)      Press the ‘Windows + R’ key on the keyboard.

b)      In the ‘Run’ windows type ’MSCONFIG’ and click ‘Ok’.

c)      On the ‘General’ tab, click the ‘Normal Startup’ option, and then click ‘OK’.

d)      When you are prompted to restart the computer, click ‘Restart’.


Method 2:


Download and run Microsoft Safety Scanner from the link to make sure you computer is not infected by virus:


Note: The Microsoft Safety Scanner expires 10 days after being downloaded. To rerun a scan with the latest anti-malware definitions, download and run the Microsoft Safety Scanner again.

Note: Any data files that are infected may only be cleaned by deleting the file entirely, which means there is a potential for data loss.


You have also mentioned that the computer is slow while booting, I would suggest you to repeat Method 1, disconnecting all the external devices connected to computer except keyboard and mouse.


Ways to improve your PC's performance


Windows hangs or freezes


If the issue still persists, please contact your hardware manufacturer for further assistance.

Hope this helps to fix the issue, if you have any further queries, please feel free to post. We are here to help you.

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Question Info

Last updated February 4, 2021 Views 24,239 Applies to: