We use Puran here on XP, Vista 32 and Win7 64. It works perfectly on all 3 systems and is very fast if you don't use all of the additional options every time. The Intelligent Optimizer only needs to be run at most once a month if even that. Personally I run it with only the first 2 options selected, optimize directories and fill gaps. I only use the full optimizer once in a while and hardly ever let it do the free space for temp files option. If I run a boot defrag, I don't choose any of the extra options since I only do that if the MFT, registry, or page file get fragmented.