In my own lab I run Windows XP and Linux Fedora 3 clusters. All our C++ code runs interchangably on either system. There are just a couple conditional compiles. These are mainly for detecting the number of CPUs on each node and for including various MPICH2 definitions, depending on a Windows or Linux build.

We are attempting to get IDL cluster code to run on Windows systems. Thanks to code out of Princeton, we can get that to work fine on Linux clusters. From what we can tell, there are several IDE-driven changes that have to be made to the C-code infrastructure. But, we expect to achieve the same portability for IDL cluster code as we have for C++.

The MPICH2 website has a specific download for implementing MPI on Windows systems.There is a bit to learn about configuring a Windows cluster network but that is not very difficult actually.

Good luck to you. Lets hear more about your experiences.