First check if the setting <setting name="Counters.Enabled" value="false"/> is set to false. It is found in the App_Config/Sitecore.config.
Moreover, a Sitecore application pool user (most probably Network Service user) has to be a member of the system “Performance Monitor Users” group to have access to the mentioned registry key. Adding the user to this group and restarting IIS should solve the problem.
What you need to do is add the duser of the app pool to the Performance Moniter Group.
Click Control Panel,
Double-click Administrative Tools,
Double-click Computer Management.
Select Performace Moniter
Add Appool and Network Service to the account
Select Performance Log Users
Add appool and Network Service to the account