Microsoft has posted a free trial of Virtual Server 2005 R2, the latest version of the Redmond, Wash.-based developer's virtual machine software that went to manufacturing in mid-November.

Virtual Server 2005 R2, or "Release 2" in Microsoft's nomenclature, sports improved performance, support for failover in case of hardware failure, clustering of virtual machines on a single host or multiple hosts, and formal support for Linux. There is also a version built for 64-bit Windows; Virtual Server only ran on 32-bit Windows Server.

The earlier Virtual Server did handle Linux, but R2 marks the first time that Microsoft's formally extended support to the operating system in the virtual machine software.

A 180-day trial version of Virtual Server 2003 R2 Enterprise Edition can be downloaded from Microsoft's Download Center in either 32-bit or 64-bit versions.

Microsoft acquired its virtual machine technology from Connectix in early 2003, and released its first product, Virtual PC 2004, in November of that year.

Also on Tuesday, Microsoft announced that until June 30, 2006, customers who purchase a license for the just-released Windows Server 2003 R2 Enterprise Edition can license Virtual Server 2005 R2 for $99. The normal price for Virtual Server 2005 Enterprise is $199.