At the end of the Create a Virtual Windows Domain with Virtual DMZ Diagram (Part 1) my virtual network now looks like this.
The two IP addresses listed against the XP machines are the dynamically allocated addresses handed out by the DHCP server. The default gateway listed will be used to communicate with a different subnet. The subnet will be created in the next part of the network build.
The Windows 2008 Server has the Active Directory Domain Services, DHCP Server and DNS Server roles installed.
The IP range for the DHCP server is 10.0.0.20 to 10.0.0.40