Currently, on my host machine I am running Windows 7. I have VirtualBox installed, and I'm trying to network Windows 2003 and Windows XP as virtual machines. Is this possible? I've set up the Domain Controller which is (10.0.0.2), but when I try to connect Windows XP (10.0.0.3) it is unable to find the domain. I also tried to ping one VM to the other to no avail. I have them set up as "internal network" in the VM network configurations. Tried Googleing and looking at VirtualBox manual with no luck. Any advice would be greatly appreciated. Thanks!

Do you have any other roles on that server setup?

Virtual box allows fro bridging of a network connection and for NAT. Except for blade type implementations it is not a good practice to run mutable virtual machines from the same computer simultaneously especially if one will be used as a server including a domain controller.