It is possible using WMP to convert .mp3 format into .wma (and vice-versa), if you have the capabilities (in which I currently have). Yes, it appears that LW only plays .mp3 format. It can play .m4a format, but you have to have a player capable of playing in that format (which I don't think I have at the moment). Originally, whenever I would put CDs on my computer, the tracks would be in .cda format. Now that format can't be played (or so it was until I was able to convert it into another format).