Some Windows applications add buttons to the control box, which apparently is the name for the group of minimize, maximize, and close buttons. One such application is Skype, which has a button for switching from a one-window-that-contains-everything mode to a one-window-per-conversation mode and vice versa:
I'd like to know how you can do this. I've looked around and can't figure out how. I assume it would require P/Invoke and the Windows API, but I'm not sure what function I'd use.