When you download a mobipocket book, you'll need a PID. It doesn't really matter where you get it from, as long as it's valid (as you'll be stripping the DRM anyway). You can get it from any installation of mobipocket reader. Once you've that PID, you can do away with the installation (just remember the PID...) The PID I'm using right now, is from my old PDA, which I don't use anymore, for instance...
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http://www.ebooks.com/help/troublesh...mobipocket.asp)