vpn connection to nt server

I have 1 ntserver running sp6.
Loaded are TCP\IP and PPTP.
2 nic cards installed one on the Internet and one on my internal network.
I can login to the server via VPN.
But i am unable to communicate with the internal network from the client vpn user desktop. (ie-Ping )
i do not have pptp filtering on.
How do i route my vpn client over to the resources on my internal network?