When a hard drive fails the most important thing to do is listen for abnormal sounds. If you hear sounds like clicking or grinding it is time to power the drive down and call an expert.
Clicking sounds indicate that you have the symptom of a failed head assembly. The concern here is that a failed head can scratch into the platters and cause media damage. The image above shows the effects of heads scratching into the platters. The dark rings you see are media damage. In many cases media damage can leave your hard drive unrecoverable.
Grinding sounds indicate that the hard drive has sustained media damage. The grinding you hear is the heads going over the media damage on the platters.
Media Damage is what we hope to avoid. That is why professional Data Recovery Companies always ask the same questions. If you hear either of these sounds immediately power down your hard drive. Only professionals can recover hard drives that click or grind. One of the reasons is that in most cases a clean room is needed to work with these issues. Not to mention the experience that is required to replace a head assembly or swap a platter stack.
Companies like 24 Hour Data offer a Free Quote for Data Recovery and a No Data, No Charge policy. Always avoid companies who charge to diagnose a Data Recovery. Also, stay away from Data Recovery Services who charge you if they do not recover your data.