When viewing shared folder contents users should be able to see only those subfolders they have access to

When you have shares for multiple users, each of whom have permissions to different subfolders in that share, you might want to filter the view that the users would only see those contents which they can access.

To achieve this on Windows Server 2003 you'll need to install Access-based Enumeration.

When installed right click on the shared folder, go to the Access-based Enumeration tab and check the Enable access-based enumeration on this shared folder checkbox (screenshot).
Click Ok.

Downloads:
Windows Server 2003 Access-based Enumeration
Documentation