IIS and folder access

I am trying to configure a virtual directory using existing asp files. It just brings up a menu that in turn brings up a list of folders for users to upload and download files. Basically a simple ftp type situation. I need to use windows authentications for access. When the desired folders are on the same server as IIS it has no trouble. When I put the folders on another server, the only way I can get the folders is with anonymous access turned on. Is it the programming or permissions. I have tried everything. Does anyone have a clue?