Quote Originally Posted by Elroy View Post
Personally, I've never used the "partially checked". But the one place I remember them being used with good use is the VB6 IDE installer, where you select the options to install. A partially-checked checkbox indicates that there are several sub-options to consider and that only some of those are checked.
That's actually an excellent example. So use it to inform the user but not to actually do anything in your program.