The Audi Multi Media Interface (MMI) is essentially a souped-up radio that also includes support for MP3 devices, GPS devices, voice-command support and a host of other features. It is not the most user-friendly device ever created, but it serves its purpose well enough. Until it crashes, of course, at which point you may need to perform a hard-reset in order to get the MMI back functioning correctly. The hard-reset process is similar to the "Ctrl+Alt+Delete" function found on most home computers.
Press and hold the "Setup" button on the MMI control panel.
Keep the "Setup" button held down, then press and hold the button atop the large knob in the center of the MMI panel.
Hold down both buttons, then press and hold the button immediately to the upper right of the large knob. Keep all three buttons held down until the MMI console resets.