Method 1 a) Click Start. b) In the search box type services.msc c) Right click Diagnostic Policy service and Go to
Properties. d) Select Automatic under Startup type. e)Click Start. f) Click Apply and OK. g)Restart your computer.
Method 2 You may run System File Checker tool.
How to use the System File Checker tool to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7 http://support.microsoft.com/kb/929833
Method 3 You may perform clean boot to see if any service is causing this issue.
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7 http://support.microsoft.com/kb/929135
Note : After troubleshooting follow Step 7: Reset the computer to start as usual