I hope I'm wrong, but it sounds like that drive may've bitten the dust. You could try putting it in another computer or enclosure to see. If you manage to get it working, I'd sure want to copy anything that's on it to another hard drive. If the drive's bearings have worn out, there's been a head crash, or some other problem caused it to die, the only way you'll get its contents is via a very expensive recovery procedure. Personally I never leave valuable data in just one place because these things can and do happen. Unfortunately Murphy loves technology.
Last night I was using my external hard drive. While using it I accidentally removed the wire without clicking on safely remove hardware. When I reconnected it the computer wouldn't detect the external hdd. I tried the disk manager way but to no avail. The light on the external hdd turns on and the disk inside runs but the computer doesn't detect it. I tried on a different computer but the results are the same.
Please be informed that the hard drive is out of an acer laptop which stopped working. So I took the hard drive out an placed it in an external casing. It used to work really well and there is really important pictures and videos on that hdd. Kindly help me get it back.