How to reset the Audi A4's media system?

I recently purchased a used Audi A4 and the media system seems to be continuously crashing. It's not responding to any commands and I can't even turn it off. What's the best way to reset the system?

To reset the media system on an Audi A4, press and hold down the 'MODE' button and the 'SETUP' button at the same time for approximately 10 seconds. This should reboot the system and clear any crashes or errors.

You can also perform a factory reset on the media system by going into the settings menu and selecting 'Reset to factory settings'. Keep in mind that this will erase all saved settings and preferences.