Does it spin, as well as clicking?
If there's no spinup, and no other hope, a sideways tap as it's powering up, or holding it and twisting sharply in its horizontal plane, may break loose a stiction problem. But even if you do get it to start, the only thing to do is to get anything off that you can!
I could be wrong - stiction may be confined to older drives, as modern drives lock the heads away from the surface when parked.
Dear me, have 40Gb drives been out long enough to be out of warranty? - must have been hellishly expensive to start with!