I was not sure how to word the title because I don't know where the issue is, if there is one. On my desktop I use Piriform Defraggler. The operating system is XP SP3 x86 and I've got 2 HDD's which run independently (no raid). After I defragment, I either get the message that there are no more fragmented files, or else I have only a few MB of fragmented files. I was using the same Piriform Defraggler on notebook in system specs. Many files don't get defragged at all, the defragging ends and I still have between 25 and 32 GB of fragmented files, which is an enormous amount! Practically most of the little squares showing the sectors are coloured red! It isn't because of a space problem, I have 200GB free HDD space. Is it because of Vista? Or because of a 64 bit system? Or because of the Raid0 (I guess with Raid0 every file has to have at least 2 fragments?) Do you suggest another defragmenting program which might work better in my case? Thanks!