Lan to Lan Connecitivity based on VPN

I have estabilished the dialup VPN connectivity between NT machine to NT machine but the problem is that the Lan behind the VPN server
is unable to ping the VPN server.
In other words, how LAN user connect the VPN
server after estabished the VPN connectivity
or what settings are required for LAN to LAN connectivity after VPN established.
Please let us know very urgent