Do you know for sure that it's the Drive itself and not the Caddy. Have you tried taking the drive out, connecting it directly to the PC, and listening to hear if there's any activity.
My drive failed and was not recognised. The PC wouldn't boot, but the drive's platters were still spinning. I bought a new drive and reinstalled Windows. Then I used 'GetDataBack for NTFS' and it recovered practically everything from the failed drive.
Fast losing patience with these devices, I had a WD "my Book" 320GB external drive and it failed about a month ago, you know, the dreaded clicking noise and not being recognised in windows, I have just spent many hundreds of pounds getting the data recovered with "On Track Data Recovery" home user. After an initial inspection for £50+vat it was diagnosed terminal after a mechanical failure and they give you the option whether or not to proceed further. A great service, with communication either via email or phone and no menus (when you call them) and they put the recovered data onto a Fujitsu HandyDrive III 250GB mobile HDD which works straight off a mini usb, power and all.......but be warned, it doesn't come cheap, depending how much data you have to recover.
The Fujitsu works fine, no noise, no heat and is very small so it sits on a little shelf on my desk just above my tower unit and comes with password protection software