Microsoft has released a public beta of Windows HPC Server 2008
>> Windows HPC Server 2008 Beta 1
Windows HPC Server 2008, the successor to Windows Computer Cluster Server 2003, is based on the Windows Server 2008 operating system and is designed to increase productivity, scalability and manageability. This new name reflects Microsoft’s readiness to tackle the most challenging HPC workloads.
>> Windows HPC Server 2008 Beta 1