I did test this drive extensively with hard drive diagnostic software I have, and it passed without any problems or faulty sectors.

No bad sectors and as quiet as ever

I think, it remaps not readable sectors, more and more and finally has reached the limit.

The second drive I received seemed to work fine, at first, but is now showing signs of rapid failure (steadily increasing numbers of bad sectors being reassigned), Would not purchase again.

, it has bad sectors and the Motor started failing

During this time, the disk encountered several write zero errors indicating that the sector is bad.

Works great as a cloned drive (sector by sector) stored externally, so that if anything happens to my main drive, I can just literally pop this one in and keep going.

The WD5000AAKX has worked well, it has been worked hard, it still has not developed any bad sectors, and I have been happy with my purchase from Amazon.

Not much to say except it hasn't failed, or developed and bad sectors

I first tried a 2T drive which works as a secondary drive on my HP computer but found that the computer wouldn't boot on the enhanced format