External harddrive for the 360?



I am able to stick in my 16 gig thumb drive into my 360 and able to get my music and video’s, my question is when i try to plug up my 320 gig external hard drive to the 360 it won’t see it.Does any one know why or i can get this to work?I’m only asking because i have the media center on my laptop on the network when i turn on my surround with wireless speakers it knocks out the connection. thanks