The increasing number of clusters built by commercial, off the shelf hardware shows a new trend in scientific computing. Within this movement is the propagation towards Windows NT as an operating system on PCs. The UNIX environment and Windows NT differ in terms of administrative issues as well as programming techniques. In this paper, we describe the modification of PVM (Parallel Virtual Machine) to enable interoperation with WIN32 (Windows NT 4/5 and Windows 95/98). PVM provides the functionality to harness the computing power of an WIN32 cluster environment. Our migration from UNIX to the WIN32 architecture not only shows where porting existing software is easy and where more generic modules have to be designed, but also the limitations.