You need to create an address pool on the NVR (Nortel VPN Router) and then associate that address pool with your IPSec profile/group configuration.
Assuming you are configuring an IPSec tunnel you should get two IP addresses. When the tunnel is up your administrator (you?) needs to configure and allow either split tunneling or inverse split tunneling. By default (without split tunneling) the PC will start routing all traffic over the IPSec tunnel so the only thing you can communicate with are devices on the VPN or the other side of the tunnel.
Good Luck!