Windows Vista/2008:
winmgmt /verifyrepository
winmgmt /salvagerepository
Windows XP (Requires atleast SP2):
rundll32 wbemupgd, UpgradeRepository
Windows 2003 (Requires atleast SP1):
rundll32 wbemupgd, RepairWMISetup
Other versions (Note it will reset the ICS and ICF configuration):
winmgmt /clearadap
winmgmt /kill
winmgmt /unregserver
winmgmt /regserver
winmgmt /resyncperf
net stop winmgmt
del %windir%\system32\Wbem\Repository\*.* /s
net start winmgmt
%windir%\system32\wbem\wbemtest.exe