I'm fairly confident that I got this to work before - but I recently ripped a CD to my work laptop using Windows Media Player - I plugged in my 9700 USB and dragged and dropped the music files - I can see the folders and files on my 9700 but when I go to play it I get an error message indicating that it cannot play it or its the wrong file type.
I did some searches and from what I've seen; I should be able to play them.
I don't know why you can't play them. I have some wma files on my media card and they play fine. You can rip to mp3 with Windows Media Player. You have to change the setting because wma is the default.