How can you transfer music from your android phone to a windows computer?

ok i opened the music files and put it in my playlist on windows media player. the songs play when my phone is PLUGGED in my computer. when i unplugged it, it didnt play the songs anymore, and a window popped upped saying there was a error playing the song every time i try to play it. what is the problem???? and... show more ok i opened the music files and put it in my playlist on windows media player. the songs play when my phone is PLUGGED in my computer. when i unplugged it, it didnt play the songs anymore, and a window popped upped saying there was a error playing the song every time i try to play it.

what is the problem???? and how do i do it correctly????