In conjunction with Windows Server 2003, Virtual Server 2005 R2 provides a virtualization platform that runs most major x86 operating systems in a guest environment, and is supported by Microsoft as a host for Windows Server operating systems and Windows Server System applications. Virtual Server 2005 R2?s comprehensive COM API, in combination with the Virtual Hard Drive (VHD) format and support for virtual networking, provide administrators complete scripted control of portable, connected virtual machines and enable easy automation of deployment, and ongoing change and configuration.

http://microsoft.com