As a novel approach to software maintenance in large clusters of PCs requiring multiple OS installations we implemented partition cloning and partition repositories as well as a set of OS independent tools for software maintenance using entire partitions, thus providing a clean abstraction of all operating system configuration state. We identify the evolution of software installations (different releases) and the customization of installed systems (different machines) as two orthogonal axes. Using this analysis we devise partition repositories as an efficient, incremental storage scheme to maintain all necessary partition images for versatile, large clusters of PCs. We evaluate our approach with a release history of sample images used in the Patagonia multi-purpose clusters at ETH Z?rich including several Linux, Windows NT and Oberon images. The study includes quantitative data that shows the viability of the OS independent approach of working with entire partitions and investigates some relevant tradeoffs: e.g., between difference granularity and compression block size. For a 2 GByte Windows NT partition our repository system enables the storage of nearly a dozen generational images or several dozens of customized images within the storage budget of twice the image size. The partitions can be replicated and transferred to a large number of PCs with our Dolly cloning tool. At present, our system is a modular university prototype based entirely on open source software, and most parts of it are in daily use to maintain our CoPs and Patagonia clusters at ETH.