Put the hard disk into a new enclosure.
I have a Lacie 750 gig hard drive that use to edit videos on. Now it only half works. When I turn on the power switch, regardless if the USB is plugged in or not, the drive starts spinning, clicks and then stops spinning as if turned off. The light remains on. This happens every time now and is not detected by my Macintosh. It use to work until I casually moved the drive from my home to my office, How could Lacie be so unstable.
Any ideas of what to do?