Don't buy hard drives from Amazon.
I ordered two, and they arrived through the post in a cardboard wrapper with no padding. The fall from the letterbox to the doormat must have been transmitted directly to their delicate internal mechanisms.
Unsurprisingly, the WD diagnostic program reported multiple errors on one, and I'm certainly not going to entrust any data to either.
Having encountered this problem, I googled it, and of course I'm not the only one. By any means.