SATA hard disk problem?

Do you have partition in that WD? If you do try moving all files into one partition and format it. I know that it might take long but there's no other way. Once you formatted the empty disk, transfer some files into it and see if the loading continues to take forever and ever. One other possibility is that you have a virus inside it... probably not just one. Try scanning it, you might detect Sality or Conficker. The best solution is to completely format the disk but it's hard to backup all of the files if it takes forever to load so one other possible solution is just format it and try recovering files using Recuva and hopefully you can recover it.