Transfer Music From External Hard Drive To PC?

I have recently purchased a new computer and storeed all my files from my old computer onto an external hard drive, I have successfully transferred all my files from the external drive onto my new computer with the exception of music.

The way I did this was to open my external hard drive and at the same time opened Windows Media Player on my computer and dragged the files from the external hard drive onto the new computer, everything seemed to be ok, all the music was organized in genre and albums titles etc, however when I tried to open a file to play a window came up telling me that the file was empty, I know that the music files can be playe3d on my external harde drive.