Well ok, maybe I overdid, but you'd understand helping here
Thing is that most popular stuff is filled with static noise, those files are originally coming from RIAA organisation to discourage P2P and they are all at the 128kbps bitrate. If you want to play music in iTunes, just inactivate the LW media player in Options -> media player, uncheck then apply. Go in library and double click on songs, they should open your default music player which should normally be iTunes. Voilà.
Bonne chance