The new version of Windows HPC Server supports using Windows 7 as a compute node in the HPC cluster. The workstations running Windows 7 can be included in the cluster thanks to the new feature called Desktop Compute Cloud (DCC). DCC administrators can specify particular hours of the day to use workstations in the cluster, for example, every night after 7PM. Of course if users are logged in and still working, the workstation won’t be used for computation.
Other two major improvements are in the application performance and in the use of multicore processors.
Read the announcement on TechNet Blog.
High Performance Computing Info 