It seems that I cannot drag and drop the images with my registration form on BuddyPress.
I do not have Contact Form 7, nor the other plugin mentioned in the FAQ.
Incidentally, I cannot find the menu which enables me to select which forms of captchas I want to use. (For example, I want to disable "fun" - there's something wrong with dragging a knife to a shower on a church website.
The main problem, however, is as I have described - I cannot drag/drop the images.