When should you replace your hard drive ?
 

It is usual that after few years , your hard drive read and write speed decreases . We use HDTune to check our HDD stats .

But it might be also that the write speed was 40MBps and now its no more than 3MBps . You should take up this issue seriously . The reason for this is that now its time to change your Hard Drive .

Now if you ask why ? then the answer is that first of all bad sectors might be come a usual for your hard drive . Your Computer could even seize to work .
Formatting the computer hard drive may solve the problem for a small period . I know all this because it happened to my laptop .

The Right Steps that you should follow
Make backup of your hard drive and get a new one .