When you use the System Monitor tool, some counters may be missing or do not contain counter data. The base set of performance counter libraries may become corrupted and may need to be rebuilt. Additionally, you may need to rebuild any custom (.NET Framework application created) counters or any extensible counters.

This behavior may occur if certain extensible counters corrupt the registry, or if some Windows Management Instrumentation (WMI)-based programs modify the registry.

This KB article describes how to manually rebuild the performance counter library values.

How to manually rebuild Performance Counter Library values