Allows an administrator to define the startup mode (manual, automatic, or disabled) as well as the access permissions (Start, Stop, or Pause) for all system services.
If you choose to set system service startup to Automatic, perform adequate testing to verify that the services can start without user intervention.
For performance optimization, set unnecessary or unused services to Manual.
Computer Configuration\Windows Settings\Security Settings\System Services
Only Windows XP SP2, Windows Server 2003
System Services policy settings are not registry keys.