This awkwardly named command appears only if you’ve installed Service Pack 1 or 2. It’s actually just a shortcut to the Set Program Access and Defaults panel of the (equally clunkily named) Add or Remove Programs control panel.

Its purpose is to let your specify which program (not necessarily Microsoft’s) you want to use as your Web browser, email program, instant-messaging program, Java module, and music player—a choice offered by Microsoft to placate the U.S. Justice Department. Details are in Section 5.10.6.