Wd passpord 500 gb hard drive not opening

Hello,
sir...i fetch my 500 gb wd hard disk and purchased a case for using as a portble hard disk...it worked for few days...but now it is showing in my computer...but there is no storage details below the local disk logo like before....right and left clicks are applied...but after a few minutes..showing that this pc is not responding.....plsss sir plsssss help....