Buy a replacement HDD and get cloning software. Install the new drive in your machine with the old one. Clone the failing unit to the new one as quickly as you can. If the clone has a few bad files, work to fix the clone. Do not take the time to fix problems on the failing unit before making the clone copy.
For free cloning software for a new drive either from WD or from Seagate, see my post here:http://www.tomshardware.com/forum/272445-32-copy-windows-hard-drive