We currently have 2 physical 2003 domain controllers, another member server that provides a few web and print services, and another member server that runs our security system. All run Windows Server 2003. I would like to upgrade our domain to 2008 in January and was thinking it might also be a good time to virtualize these 4 servers (2 DC's, 2 Member Servers) onto one virtual server running VMWare. These are pretty "low use" machines and were my best candidates for virtualization. Is there any issue with virtualizing domain controllers? I already have a robust Dell R900(64GB RAM) in place running VMWare ESXi and just waiting to be put to good use....This would also clear up 6u in my rack! If I can do this, then the next step would be to upgrade Exchange 2003 to 2010 and then the rest of my physical member servers to 2008.