If it's an internal HDD, put it in an external enclosure and see what this PC and another PC think of it.
If it's an external HDD, try it on another PC. If it fails there also, take the HDD out and put it in another enclosure.

If it still fails, find a data recovery company and ask them to get as much of your files off to a new hard disk as they can (and you are willing to pay for).
Of course, if you have a good backup of all of the data on this disk, there's no need for data recovery and you can just buy a new one and fill it from your backup. That's much cheaper.