I hadn't used it in about four months... It worked perfectly time the last time I used it. But when I tried to use it today, my computer would not detect the device (actually, my computer DID detect it... and "installed device drivers" even though I had used it previously, but would not show up in my Explorer window). I tried rebooting... Same result. I tried another computer... Same result. One thing that's changed is that whenever I power up the external hard drive, it makes a "clicking" sound every 3 seconds. What should I do?
Clicking noise may well be the "click of death" due to the heads trying to park and smacking the stops -- I would RMA the drive, as I have never had success fixing the issue any other way in this situation.
The only other thing to check is whether the drive has a drive letter in disk management and if not whether you can assign it one, but more likely the former problem.