Found this wonderful post by Vincent Wang at TechNet which has resolved various WMI errors on Windows XP workstation (re-register and re-compile part at the end): Thank You Mr. Wang!
Please perform the following steps to troubleshoot the issue:
1. Log onto Windows 7 with an administrator account, click Start, type services.msc in the Start Search box and press Enter.
2. In the right pane of the Service console, locate and right-click Windows Management Instrumentation, and then select Stop to stop the service.
3. Start Windows Explorer, and then locate the %SystemRoot%\System32\Wbem\Repository folder.
4. Backup and delete all the files in the %SystemRoot%\System32\Wbem\Repository folder.
5. Restart the computer.
The files that were deleted will be re-created when the computer restarts.
Note: The Windows Management Instrumentation service starts automatically when you restart the computer.
If the issue persists, please re-register WMI DLL files and re-compile WMI mof files to check if the issue can be resolved. Here are the detailed steps:
1. Disable and stop the Windows Management Instrumentation service.
2. Right-click Command Prompt and select Run as Administrator.
3. In the Command Prompt, type cd %windir%\system32\wbem and press Enter.
4. Type for /f %s in ('dir /b *.dll') do regsvr32 /s %s and press Enter to re-register WMI DLL files.
5. After completed, type for /f %s in ('dir /b *.mof') do mofcomp %s and press Enter to re-compile WMI mof files.
6. After that, type the command wmiprvse /regserver and press Enter.
7. Start the Windows Management Instrumentation service and change the Startup Type back to Automatic.
Hope this helps.
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