I have my music downloaded at least that is what the computer says, however when I try to listen to the music my MP4 player says empty disk... PLEASE help... how can I listen to my music

What player is this... an Apple, A Zune, or any of the generic types?

MP4 is a video, MP3 is typically audio.

Ipods have to import the music via software or it won't play, while the generic MP3 players you can simply move them like a thumb drive.

Not all play videos (MP4) in their native format... give us some more details please.

My doesn't my mp4 hear