Ok, no, this isn't a drm issue. Latest Calibre version (Although I've been using the portable version, maybe related to the problem?). I can convert from an azw3 fine, and the resultant mobi is viewable. However, I can't actually open the azw3 itself, I just get a windows message about an unknown filetype. So I'm guessing some sort of file assosciation hasn't been set up properly, possibly caused by my using the portable version instead of the installed version? Any thoughts? I'm kinda feeling like an idiot that I'm having to ask something like this, I should really know better
.