also ..hobo & blondie,
when you add files to your media player(realplayer)(winows media player) (i-tunes?)the file type changes to whatever you set the player to. it will then burn according to which file type is in there. my realplayer has mp3, windows has wma, etc.

one other thing, you might try changing the "burn speed". sometimes cd players won't play because of the speed the cd was burned. usually older cd players.