If the HDD is not responding even when slaved, it's most likely a physical problem inside the HDD.
Sorry, but there's not much that can be done for that.
If even one tiny chip develops on one of the disks inside your HDD, the little arm that reads the info on it will catch it and make the chip bigger, and the peices will move and catch other places causing scratches and more chips etc etc.
Its a tough way to go, but it pretty much eats itself alive with every rotation of the disks.