A clicking hard disk could be just a hard disk that doesn't get enough power. Try it with with an Y-cable on a powered USB hub. If that doesn't work, it's time for professional help. It's your choice to determine if the lost documents are worth more than their invoice (then do it) or less (then don't).
I recently bought a 3.5" HDD SATA to USB 3.0 enclosure to read two of my internal Samsung 320GB 3.5" SATA HDDs that I saved from a fire in March 2014. The fire didn't reach any of my things, but unfortunately soot and smoke had engulfed the room and it filled with smoke particles causing both my hard disks to be stained with soot. After the firefighters had left, I took it off my CPU which sadly already had the covers open and then cleaned the stained bit with a mildly wet tissue. Thankfully the PCBs were not damaged by the smoke as it was covered by the drive bay brackets. I wrapped it up in cling wrap and loads of bubble wrap and left it with my roommate along with the rest of the other things that I could salvage. I finally took it with me back to Singapore last xmas 2014. Long story short, sorry...
The enclosure I bought was a good brand, and I connected it to try to read the first rescued hard disk (HD321KJ). To my horror, it started clicking so loudly I had to turn off the power. Then I waited for a while and I turned on the power, it didn't click so loudly, it was actually trying to read before having a steady click-click every 3 seconds.
Here's what happen to the first hard disk (HD321KJ):
The laptop could detect and install the driver. But it wouldn't show on Computer.
When I plugged it in again, it indicated in the taskbar balloon that the USB malfunctioned.
The second hard disk (HD322HJ):
The laptop detected and installed the driver smoothly, it read within seconds. There was no clicking sound and I could actually read all my files (THANK GOD!). Coincidentally, this is the hard disk that contains my Win 7 OS.
I'm really worried about HD321KJ as it contains all my design work and precious photos!
What could be the cause of the clicking drive? As I didn't drop the drives, they were still in the CPU when I came for them. I know it is definitely a head crash, but the other hard disk works perfectly, even though they were both in the same boat.
And how do I resolve this issue? should I replace the PCB? I really would hate to go to a recovery lab as I know it's going to cost thousands of dollars. I've seen videos of people trying to fix the head crash, I was wondering if I could do the same. Please advice.