Navision Application Server

I am trying to setup NAS and have read many of the help documents reccommended here. When installing, I do not get any prompts for the database, server, startup parameter, etc. When I rerun the installation and get the Repair choice, I get this message: Error 1923. Server MBS. NAS could not be installed. Verify permissions. What does this mean? Are there some rules on where NAS is installed to relate to the version and database I want to use?