I would like to start a "Corner Discussion Forum" about Windows (NT) Services

Hello there. I am writting from Spain and I am working with Windows (NT) Services at the moment. I have done a service and in the "OnStart" function I have created a process to launch a ".exe". the point is that it launches in background mode. How can I launch in a NO-background mode? I know there is in "Control Panel\admin tools\services\" a posibility to do it by rigth clicking in a service and in properties, in the LogOn, you can tik the box taht says "Allow service to interact with desktop" How can I do tha same thing in program code?