Loginf failed for NT AUTHORITYSYSTEM

Hi All,I have windows service that accesses database. I need that service running before user logged in. I set the service running under LocalSystem account which corresponds to this user name NT AUTHORITYSYSTEM. I added this user under Security/Logins and mapped to database I need to access. I also set default database for that user as my database. I gave permission to read database for that user.I also run these procedures EXEC sp_grantlogin [NT AUTHORITYSYSTEM];GOEXEC sp_grantdbaccess [NT AUTHORITYSYSTEM];GoMy connection string isIntegrated Security=SSPI;Database='**database**';Addr='**SQLSERVERNAME**';After failing with all these steps I tried to switch my service running under mycomputeradministrator and sets the same permissions that I did for NT AUTHORITYSYSTEM. Still no luck. Login failed. Of course I do not get this error when I log in and start service from Services console.I am running Windows 2003 server and SQL server 2005Anyone could help me to overcome this issue?Thanks a lot in advance,Roman