VPN and Folder Access

I'm currently doing a Diploma of Information Technology. We have set up a
model network to work on in the classroom. It uses one common DC at the
forest root and then our own servers are DCs of their own child domains. The
servers running are Microsoft Server 2003.

On our servers, we have setup a list of domain users and allocated them hard
drive space on the server. Permissions have been setup so a user can only
access their own user folder, no one elses.

Logging in as a user on the Windows XP workstation confirms that the user
only has access to their folder, no one elses.

We have also setup an intranet website, which provides remote access to user
folders. The folder security works here as well, a user can only access their
own folder and no one elses.

We then setup a VPN connection on a computer not part of the domain. My
users can connect to my server using the VPN connection and they can see the
folders on the server. The problem is that they can not only access their
own, but other user's folders as well. It's like the permissions just dont
exist, they can read, write, delete other user's documents.

My fellow classmates have also setup a VPN connection to their servers.
Their permissions are working properly while mine are not.

I've tried uninstalling the Remote Access role on Server 2003, then
reinstalling it using the same method my classmates used. The problem still
remained. My teacher has looked through my server and he cannot find the
problem.

The only theory we can come up with is somehow, when the user logs in
through the VPN connection they are given administrator rights... Even though
in AD they do not have them.

The problem is simply that a user can connect to the server through VPN and
access other user's folders and files, despite the permissions on them.

Any help would be appreciated.