Same thing happened to me a couple times with WD external drives. What you are experiencing is the "click of death" (Google it). Only two ways to get your data back. Either send it to a lab or try this quick fix:
Put the drive in a plastic bag in the freezer for a few hours. This may cool down the unit and 'unstick' the drive.
That's the only DIY fix I know. But here's a Tip: stay AWAY from Western Digital. All my external drives are Toshiba now.
Good luck! Glad there's no serious data loss.
