VPN – cannot find my computers

I have just established a VPN connection between my work and a home office. The connection is between two firewalls that runs the IPSec protocol for VPN connection. The internet connection is also accessed through this firewall. The VPN tunnel is established and I can ping all computer on my HQ LAN from my home office.
When it comes to accessing the computers from the MSWindows I can only connect to workstations that is not a member of our Domain Controller (NT4 small business server). I am not very good at managing NT Network so therefore I post this message to you all if you can help me to solve this problem. A lot of employees will be happy if we can make it happen.