My system hard disk is not working properly

My system hard disk is not working properly from previous 1 month.
When I copy any song in my computer and then try to play it then it generates an error for me.
Also,when I generate any word, excel or access file in my system after some time when I try to open this file then some strange type of writing appear.
Then I buy one Window DVD from the market and try to install it but I am receiving below error can any one tell me what is meaning of this error?

Boot sector
Status: Bad
Backup boot sector
Status: OK
Sectors are not identical.
A valid NTFS Boot sector must be present in order to access any data; even if the partition is not bootable.
