DogsWithoutWings.com Blog

If you are using Windows Vista and the Security Center is complaining that Windows Defender is not running, and when you try to start it all it does is check for definition updates, try the following. Took a few weeks to find the fix for this problem.

Note: This fix is not for Windows Live OneCare users.

1. In Control Panel/Administrative Tools/Services, find the Windows Management Instrumentation service. Right Click, then select properties. Set the 'Startup Type' to 'Disabled' and press 'Stop', then 'Apply' (Don't close the window).
2. Delete the folder c:\windows\system32\wbem\repository (This assumes c:\windows is your Windows install directory.)
3. Go back to the Windows Management Instrumentation service window and set the 'Startup Type' to 'Automatic', then 'Apply'.
   
4. Reboot the computer and it should start showing Windows Defender as running.