the files are in mp3 format, but windows media player converts them to wav audio then i burn to cd. The cds work perfectly in any other cd player, its just that something is wrong with my car cd player, it cant read burnt cds properly, it works for maybe 2-3 songs then the first bump i hit or if i try to forward the tracks, it says ERROR 11. So im guessing it has something to do with the cds im buying or the software im using. Cleaning the lens didnt help. I wish i could just ask the guy i buy the music cds off of what he does, cause only his burnt cds and originals can play in my ford.