Has your hard drive crashed? Does it create that spinning, clicking sound when you boot it up? It could be that your hard drive has a defective controller board.
The hard drive consists of a few basic parts: motor, platter, disk head and the controller board (PCB). If any one of these parts is damaged, then the hard drive will stop functioning. If the PCB is the only damaged part of the hard drive (due to power surge, overheating etc.), then replacing the PCB board will get your hard drive spinning again.
However, there is no way to know for sure that it is the controller board. If you really need to get your data off that crapped out drive, it may be worth $39.99 to see if PCB Solution works.
Thanks go to Ja!