I have been getting this error in the event log of one of my clients servers:

Access to performance data was denied to UserName as attempted from C:WINNTSystem32WinMgmt.exe

I first tried this:

Open the “Computer Management” app
Expand the “Services and Applications” section
Right-click the “WMI Control” entry & select “Properties”
Go to the “Security” tab
Expand the “Root” node and then select the “WMI” node
Click the “Security” button
Add the account & give it access

That didn’t work, so I found another suggestion:

1. Run regedt32
2. Select the key SOFTWAREMicrosoftWindows NTCurrentVersionPerflib
3. From the menu select ‘Security/Permissions’
4. Add the Internet Guest Account granting only ‘read’ permission

In case that doesn’t work, here are some more articles on the subject

http://support.microsoft.com/kb/226494

http://www.eventid.net/display.asp?eventid=1000&eventno=1700&source=Perflib&phase=1