When your harddisk fails the DST Short, and Long (remember to check, might give some insight) you can use the Seatools to Dos
program, to erase and repair bad sectors. However should this fail, your only option is to buy a new HDD.
(However even though it might sometimes work as nothing is wrong, it will die every single time, you try to do a backup to an ex-HDD.)
Can you explain the use of your computer, is it for gaming, or work/study?
Hope it helps.