I have Dell Inspiron  one 2320 ALL IN ONE pc with i3 model and this pc has western digital hard disk 500gb.

from past 3 or 4 days my pc mainly hard disk is so slow .  earlier it takes only 10 to 15 seconds to shut down but now it takes 3 to 4 minutes to shut down and it is also using so much ram all the time.

and then I decided to run "pc doctor" provided by dell...

it passed all the other tests but cant passed hard disk test............

IT fails in the "Targeted Read Test" and all other tests wee skipped automatically .so thick this is the root of the problem

I have Windows 8PRO 64Bit Installed on pc,and harddisk model is    WDC WD5000AAKX-753CA1...

and when test failed it then it gives an error number is  "WHD20-BQl"  written in front of targeted read test....