Hard drive fails to displays signs of power and 'winding up': It is possible that your hard disk could be properly plugged but there is no sound of the hard drive moving within its case. When you connect your hard disk to the computer and switch it on, there should be some sort of 'winding' sound that comes from it. A light indicator on the motherboard should indicate a proper connection. But if light indicators on the motherboard are not illuminating it means that the hard disk is not receiving power. What you can do is to check on the connections of the hard drive. If you are not sure of how to do it, get an expert to do it for you.
Constant clicking sound emitted from the hard drive: In this case, it is most likely that the actuator arm is broken from its locking point and is swinging freely. The constant sound is heard because it is touching other internal components within the hard drive. In such a state, the drive is not able to perform the read/ write function. What you have to do is to get a data recovery expert to recover your information.