The current configuration information for drivers and services when a user successfully logs on to a Microsoft Windows 2000 or Windows NT system. This information is copied to the LastKnownGood control set in the registry and can be used to recover your system if you cannot log on again (for example, if you add or upgrade a driver that is incorrect for your hardware configuration).
If you modify your system and are unable to log on again, you can restart your system, press F8 in Windows 2000 or Spacebar in Windows NT, and follow the prompts to reset the Windows configuration.