you also have with the nav system the ability to load a cd or the flash card and burn CD onto the harddrive and play from there. you can also use a ipod with the cable that everyone is talking about. that cable will also work with the iphone to play music through as well. All of this information is in the owners manual on how to do this. If you have questions feel free to pm me and I can walk you through the steps if you dont have the manual.
