My Computer Wont pick up my Zen Stone?

My computer wont pick up my creative Zen Stone MP3? It charges it, but doesn't show any new hardware found. Although i haven't got the installiation disk with me, i have put it into my friends computer and it has worked perfectly. I have tryed restarting my computer with my MP3 plugged into it and that doesn't work. I have tryed plugging it in when my computer is allreadt up and running and it still doesn't work. Can someone please help me and tell me what is wrong with it? thank you very much.