I believe you misunderstand services. They don't have user interfaces (UIs) like other programs. They run without any UI as background processes that are in basically in an infinite loop but with a way to break out of the loop (stop service). If you wish to have a background service that has some sort of control UI, you need to write it as two parts. The service and a UI that communicates with the service either through a shared file, pipe, or socket server/ client interface.
You should pick up a copy of Python Programming on Win32 which is an excellent reference book for writing Windows services. -Larry Bates -- http://mail.python.org/mailman/listinfo/python-list