Clusters of PC containing mostly general purpose hardware have become more and more usable for high performance computing tasks in the past few years. Clustering existing systems or extending cluster installations leads to the problem of inhomogeneous cluster installations with a broad variety of hardware and even operating systems. This paper describes the efforts of the MetaMPICH project to deal with multi-platform inhomogeneous clusters, using different networks and processor types. An approach is presented which on one hand hides the heterogeneity of soft- and hardware from the MPI application programmer, but on the other hand supports the exploitation of special abilities of single meta computing resources by providing a new MPI communicator which reflects the real topology of the connnected systems.