I've got a WD Elements 1.5 TB drive hooked to my TV for watching movies, about 2 years old. In a pinch, I used it to dump some big files on it and then I was unable to get them off. I ran TuneHD and found some errors in the back end of the drive so I assumed it was failing.
So, I ordered a new internal drive and took apart the enclosure and hooked the old drive and the new drive up to my PC directly through SATA (versus the USB from the external). I was able to transfer all of the files to the new drive, including the big files that I had trouble with before. Then, I ran TuneHD on the old drive and it showed no errors.
The only difference between the first time and second time: 1st time was the unopened external HD using USB, 2nd time was the removed HD hooked directly to SATA.