How do we configure two (2) LAN cards on one computer. One LAN card is connected to the internet via the DSL through a router, configured as DHCP. The other LAN card is to be connected via our office's IP/VPN (for email and other office online processes). I know it could be done, but I do not know how. By the way, the operating system is Windows XP.
I think you need to use XP's route tables to redirect packets based on their destination address.
Packets directed to your office you want to pick up and route via your office nic.
This is done with XPs route command.
The basic syntax is
route ADD <destination> <subnet mask> <gateway (vpn dhcp server)> <metrix> IF <interface number>
I've never had any trouble at all doing this. Windows seems to handle it quite gracefully. When your computer has two network cards, you get an icon for each one in the Network Connections window, and you can configure them separately. Traffic intended for one network (say a web server on the intranet) goes through the appropriate network card automatically.
If you're having specific trouble, let us know with a little more detail, including error messages and whatever behaviour you're seeing.