Try this:
Go to the console and type "diskpart" (no quotes)
Type "list volume"
If your drive shows up here, but has no letter associated in the "Ltr" column, all you need to do is assign it one. You can do that as follows:
Type "select volume x" where x is the number corresponding to the hard drive
Type "assign letter Q" where Q is the desired drive letter (recommend a letter between F and W, because some applications map drives X, Y, and Z for emulation)
If that was the issue, you can quit out of the console and your drive should appear in the Computer menu. Good luck!