I downloaded the aforementioned FretPet to give it a try. Fortunately it's shareware or trialware (not sure which) but I managed to download it and give it a quick try out.
The bad news; it opens up a bunch of windows and I have no idea what I'm supposed to do! I can't even figure out how to simply display a C chord. I can click on the fretboard and mark strings to 'play' and therefore draw my own C chord, but I can't get it to show me a C chord, and I feel like it should do that.
And it does all these other things in other windows and they don't mean anything to me. It looks like it should be interesting, but I don't know what I'm supposed to do! It's very frustrating. I spent a good five minutes messing about with it and was none the wiser for it.
I guess I'm going to have to actually read the documentation if I'm going to figure out how to do anything with this program, which I think is rediculous. Some of these functions should have been really easy to figure out. It should have led me in and encouraged me to use it, not leave me stranded before we even get out to sea.