My 2007 Camry comes with a radio that supposedly can play MP3 and WMA files. The manual is very vague about how to burn CDs for this. The controls have a "folder" item which seems to let you put CDs into folders on a disc and then navigate among them, which is very cool since you can obviously fit a lot more WMA songs on a 650 MB CD-R than you can with standard CD audio encoding. However, when I tried to do this, the disc is not readable on the player.

Does anyone have advice on how to burn the discs so they are usable on the car?

Thanks.