VPN IPsec: NT4 PDC wan’t let me in.

I have established a VPN tunnel between two firewalls and can browse some workstations from my home office. But the PDC is invisable to me. I have not set up any special things on the server to get to it other than I have a user with certain rights.No RAS is setup and no VPN communication is setup from the server cause the VPN tunnel is handled between the firewalls(Zyxel Zywall10 and Zywall1). Is there some setup on the nt4 server I need to do to make this work ? The workstations I see have nothing special setup on them except that its win2000. I do not see win9x machines either.

Thanks !