Topic: External HD shows up in Device Manager but not Win explorer... Help!

[OFOTD]

Another alternative is to boot from a live Linux disc and see if the drive is recognized then.that way.

Great suggestion.  FWIW, the Windows version of a live CD is called WinPE.  There are several different flavors of WinPE on the usual torrent sites.  They just allow you to boot into windows off of the CD.