Hello,
Based on your description the sound that you are experiencing is not normal. Scratching or grinding sounds on a hard drive are indications of failure. I recommend that you contact Western Digital Support in order to have this drive replaced.
You may click on the links below for more information.
http://wdc.custhelp.com/app/answers/detail/a_id/568
http://support.wdc.com/contact/contact.asp?lang=en
http://websupport.wdc.com/rdsfdc.asp?linktype=rmacreate&portaltype=wd&custtype=end&fs=&ss=&lang=en
