Re-reading this thread, we haven't answered one of your queries and perhaps made things more confusing.
'Nutchords' appears to use a minus (-) sign to indicate a note that isn't there, see my last message.
More generally, as Mark does in his message, a minus sign is used to indicate a minor chord. Personally, I always use an 'm' but lots of people write Am as A-.
Hence, when Mark wrote E-7, he meant Em7, not E without a seventh (which wouldn't make any sense, anyway!)
I remember trying 'nutchords' a while back, but I didn't like it. I can't remember quite why.
A similar, in some ways more simplistic, but in my view better shareware software is 'Chord Magic' It's DOS based so it doesn't look as pretty and it won't play your chord back to you. It does however give a variety of different possible names for any chord and lets you superimpose any scale over the fretboard so you can see how the particular chord relates to any scale.
I haven't got a link for it but any decent search engine should find you a copy.