Microsoft® Windows NT® version 3.5 and later provides new window station and desktop functionality that enables Win32 services to call USER32 and GDI32 functions regardless of the logon account in which the service is running. This new functionality enables Win32 services to make these calls while maintaining the security of applications running in the account of the logged-on interactive user.
For more information on how Win32 services use the window station and desktop support, see Interactive Services.