1. A method implemented by one or more computing devices, the method comprising: displaying an immersive shell of an operating system that is configured to support access to applications using one or more techniques; and displaying a desktop shell simultaneously within the immersive shell, the desktop shell being displayed and also accessible using the one or more techniques that are used to support access to the applications in the immersive shell, the desktop shell presenting applications that are executable in the desktop shell through windows having user-controllable frames, and the immersive shell excludes support for access to applications that are presented through windows having user-controllable frames unless the access to those applications is performed through the desktop shell.