It would unfortunately appear that the disk is faulty. Check the link below for the steps to replace it. If you need to recover your files you can contact any of the data recovery partners on the WD support page, some of them offer a free evaluations of your drive.
How to get an RMA, (Return Merchandise Authorization) or replace a defective product under warranty
http://wdc.custhelp.com/app/answers/detail/a_id/8
Data Recovery Partners
