Mp3 player download cant do?

It could be because the player doesn't support the files they may have copy protection (eg. m4p [itunes store] or wma [windows media can be protected]) or the player doesn't recognize the files eg. AAC. Look in the manual and see what formats it supports. Amazon MP3 is great as the files are in MP3(playable through practically any device) and are cheap (and legal). Try copying the music in windows explorer (send to -> F:\MP3 Player) instead of using realplayer.