Vulcan's point is good, although Vulcan, perhaps she uses the memory card between different devices, or has different memory cards?
In any case, Paula, yes, you can move them anytime. For MS Reader, put them anywhere you want. For Palm Reader, they have to be in "\My Documents\Peanut Press" either in main memory or a storage card. Moving them via File Explorer is fine. Do avoid having two copies of the book, otherwise you might see two entries...
Palm Reader's desktop "installer", BTW, is merely for convenience. I don't use it anymore -- I copy files to the memory card via my desktop's USB flash reader.
--janak