Your hard drive holds all your information. If something goes wrong with your hard drive you stand to lose all your information. However, hard drives are designed in a way that enables you to retrieve information even if it’s dead. Surprisingly all supposedly dead hard disks have information stored on it. That information is really stored on the discs that the hard drive writes information to.
If your hard drive is working and you’ve accidentally erased all information off it then you can enlist the help of commercially available software. But these software packages do have their limitations. For example if the sector that needs to be recovered was overwritten with new information, recovering data from that sector would become impossible. Also a software recovery solution cannot be used on a dead hard drive.
In cases where you hard drive just refuses to work you would need to take it to a recovery center. Here the people would dissect your hard disk and recovery your data of the individual plates that are inside the hard disk. Do not try to dissect the hard disk yourself because you could inevitably contaminate the plates hampering all possibilities of data recovery from your hard disk.