I was able to get connected to both the Domain and Workgroup at the same time.
With 2 network cards in one PC, you use a static address on the Peer-to-Peer network. And for the other NIC use the DHCP server for the domain. You may have to use a PCMIA network card as the second NIC in a laptop.
name the workgroup the same as the domain name.
Been a while since I did any of this, but let me know how you get on.