Hello, I puchased a euro - D unit on ebay. Have it installed in 2000 A6, works fine (converted the language to english) but do not know how to convert it over to read U.S. discs. It has a Germany map disc in the unit now. I have a complete set of C-navi and D-navi Audi OEM discs. Unit will not recognize U.S. discs, Can someone please lead me in the right direction ??? ....... Thanks in advance.