It's "DRM" and is designed to stop you from doing this. Since you need just that track, why not buy the CD?
I was just wondering if it is possible to get music OFF of a napster mp3 player. I've had this problem with other mp3 players too, I want to get a song off of it to use for a presentation or something and I can't get it off because the mp3 player doesn't show up in my computer. Any suggestions?