Microsoft calls it's HPC CCE.

We'll never run out of three letter words. Promise.
BIO-IT World calls Microsoft "The 800-lb. gorilla of desktop computing" and comments about our plans to "aggressive push into life science clusters". "The main HPC push from Microsoft will come in the second half of this year when it releases MS Windows Server 2003, Compute Cluster Edition (CCE). Microsoft says CCE will be a complete Windows-based HPC solution that addresses cluster setup and management, application development, and job scheduling." All the stuff they're talking about will be 64-bit (x64).
Microsoft is investing in HPC for quite some time already but with 64-bit comute power at a 32-bit price, the time is more than right to address this area even more. Learn more about CCE on the Microsoft CCE website (still hpc in it's name).