Maybe ?

I have had about 15 Externals in my time, every problem i had was the same one, the circuitboard came away from the hard drive, all i did was unscrewed the whol thing pushed it all back together tightly

Dont know if this will help with your problem....

also try to run chkdsk

http://support.microsoft.com/kb/315265 - Windows XP

http://www.w7forums.com/use-chkdsk-check-disk-t448.html -win 7

Good luck

 

You cant run chkdsk if it not detected, First check it on Disk management , whether it detect or not.? If not some times it related USB cable issue, sometimes issue with connection jack of the Cable, or Sometimes it issue happens less power . Try to use 2 usb ports to get power by from Y cable.

 

Skim through Troubleshoot: Windows Won't Recognize Your USB Hard Drive
> Check Disk Management as someone else suggested above to see if the disk is recognized (there's an example in the Guide i posted)
> If the Drive is appearing in lower pane of Disk Management but not the drive letter in upper pane of Disk Mgt or in My Computer etc. the filesystem might be corrupt. You can try a data recovery tool like TestDisk

 

@
dhanushkapg.... Yes dude.. Thanks for Helping Me Too.. That Less Power Issue Was There, That I Fixed It Now.. Thank You