The Perfmon subkey stores user-specific configuration data for Performance Monitor 4 (Perfmon4.exe), a performance monitoring tool designed for Windows NT 4.0 and earlier. In Windows 2000, Performance Monitor 4 has been replaced by System Monitor, but Performance Monitor 4 is included on the Windows 2000 Resource Kit CD-ROM for compatibility with earlier systems.

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The Perfmon subkey appears in the registry the first time you use Performance Monitor 4. You might need to run Performance Monitor 4 more than once for all of the default entries to appear in the Perfmon subkey.

The entries in the Perfmon subkey only apply to Performance Monitor 4, a tool provided only on the Windows 2000 Resource Kit CD. They do not affect System Monitor. To configure System Monitor, use the System Monitor Properties dialog box.