|Who is KHALID KHAN?|
Are you talk about an internal hard drive or external?
Can you try the drive in another machine just to rule out the drive?
can you test your power supply unit, if the PSU is not supplying the correct power to the drive then it will not be detected.
You could try getting something like a magic bridge to connect it to your pc via USB to retrieve your date.
However if the drive is not detected on the other machine, then obviously your drive is damaged, in many cases when a drive is not detected, it is usually the control board that has failed. you could change the control board and try again. If you let us know what make/model the drive is we should be able to help find the correct board.
Just a couple of questions:
Is it an internal or external drive?
did you drop or knock the drive at all?
are there any clicking noises coming from the drive?
what are you system specs?