Ah, I believe file sharing is configured elsewhere in Mac OS X Server. I haven't used it extensively, but I'm sure you can track it down with the search tool in System Preferences, or, barring that, searching the documentation.
leopards file sharing option is in the "server Preference" app. Thats in Application/server/server preference. or you can use server admin (same place). 10.4.11 just has server admin iirc.