Audi with SD card slot for MP3 does not load card, help

[Halo]

Have tried to transferring mp3 files from my computer onto Sd card and then play them in my Audi. The display shows the card being read and then reads card slot empty. Have imported direct from cd as MP3 files (160kbits/s) on itunes and then transferred onto sd card in Mac finder. Could anyone tell me if this is the correct method to create a sd card for playing MP3 files?

[Halo]

The manual states the memory cards must be formatted according to the FAT or FAT32 procedure and that the MP3 files names must end with "mp3"?