On April 3, 2006, Microsoft announced that Virtual Server 2005 R2 Enterprise Edition is available as a free download. The Standard Version is no longer available which makes sense. They also announced the availability of virtual machine add-ins for Linux, and a technical product support model for Linux guest operating systems running on Virtual Server 2005 R2. Currently only Red Hat and SuSE variations have been tested and are on the list of supported guests for Virtual Server 2005 R2.
http://www.microsoft.com/windowsservers ... icing.mspx