External hard drive not being detected

Nah,open it in device maniger,change letter path,and perform a format,or just right click quick format.

Try uninstalling reinstalling(device maniger,open that hdd,properties,uninstall) Then reinstall

I searched a while a found answers on Microsoft's website,but I tried it and it only worked on xp,not win7, sorry mate, I think that hdd is trashed, unless you can put it in a new formatted pc from start up,and then select it in bios to format(ie use it as an internal hdd) I think buying a new one is the option