The answer to my question "Windows LocalSystem vs. System" states (plz note that I am blocked there from participation in my own posts):"There is a single well-known SID for the local system. It is S-1-5-18...""Configuring a service as "Local Service" tells the service to log on locally to the workstation as S-1-5-18..."Please explain me why "NT Authority\Local Service", having SID S-1-5-19, is using the SID S-1-5-18 of "NT Authority\SYSTEM" on workstation (Windows XP Pro).Related question:AD Network Service vs. workgroup NetworkServicehttp://social.msdn.microsoft.com/Forums/en-US/sqlsecurity/thread/b93a34ac-362f-4e7d-95cc-c5b65b7920921 person needs an answerI do too