A type of radio button exists in versions older than 7.1. If you start the Example Finder and do a search for radio, you'll find a couple of different ways. Also, in examples\general\booleans.llb, you'll find some custom controls (2 Radio Buttons, 3 Radio Buttons), etc) that you can use. These custom controls are really slide controls with text labels and different graphics. Just like LabVIEW 7.1, they enable you to use a radio button control with having to write any code to implement.