seehttp://support.microsoft.com/default.aspx?scid=kb%3Ben-us%3B317012".... Using Performance Counters The ASPNET account has sufficient permission to write to (but not to read) performance counter data. If the application must read performance counter data or create performance counter categories, Administrator or Power User permissions are required.If an application must create new performance counter categories, create the categories at installation. After the categories are created, the ASPNET account can write to the counters.You can still use the Performance Monitor tool (Perfmon.exe) to monitor ASP.NET performance counters when you use the ASPNET account ..." or change userName in <processMode> in machine.config to "SYSTEM", but it is not recommended
Using Performance Counters
The ASPNET account has sufficient permission to write to (but not to read) performance counter data. If the application must read performance counter data or create performance counter categories, Administrator or Power User permissions are required.If an application must create new performance counter categories, create the categories at installation. After the categories are created, the ASPNET account can write to the counters.You can still use the Performance Monitor tool (Perfmon.exe) to monitor ASP.NET performance counters when you use the ASPNET account
..."
or change userName in <processMode> in machine.config to "SYSTEM", but it is not recommended