I have a 2001 Audi A4 2.8 Quattro and it has the single color tone Audi Navigation system that is ran through the center console screen. I push the "NAV" button in which (it is located near the parking break and the center arm rest) nothing happens. I hold all four buttons down (seperately) with the ignition started and no respose. I look in the trunk at where the 6 six disk cd changer and Audi Nav system computer is located and I notice that either A) The cd is missing and someone removed it without my notice (I used the Nav system just a month ago) B) It is jammed and it can't read the disk C) Just doesn't work for whatever reason. What is the problem? Can I download those files for theNAV cd for free if I need them or where can I find them? Thanks for your input.