Microsoft released a new whitepaper about its new virtualization platform:
Virtual Server is a Microsoft Windows®–based server application that is optimized to provide virtualization of Windows Server operating systems concurrently on a single physical server. In combination with the Windows Server 2003 operating system, Virtual Server provides a platform for implementing domain controllers in virtual machines. With this platform, you can install multiple Windows Server 2003 or Windows 2000 Server domain controllers in separate virtual machines on a single physical server. In this way, you can host multiple domains, multiple domain controllers for the same domain, or even multiple forests on one physical server that is running a single operating system.
Running domain controllers in virtual machines is best suited for test and pre-production piloting environments. With strict adherence to the requirements described in this document, domain controllers running in virtual machines can also be used in a production environment.