DC on VMWare

I have a windows XP computer on the network with VMWare installed. I also have windows server 2K3 installed on the vertual machine, and would like to create a seperate domain for R&D testing. When I set up Win 2K3 as a DC, I don’t want it to join the current Domain. However, I would like both domains to trust each other. Is this possible, and how do I do it?