Download the Windows HPC Server 2008 Trial for 180 Days

Windows HPC Server 2008 combines the power of the Windows Server platform with rich, out-of-the-box functionality to help improve the productivity and reduce the complexity of your HPC environment.

For More Details Check :
http://www.microsoft.com/hpc/en/us/trial-software.aspx

Reference: http://www.microsoft.com/hpc/en/us/trial-software.aspx