I had the same problem with an external drive.It was there on devices but wasn't recognised in explorer. My soltuion was to run diskmgmt.msc at the run command. You can then see your drive. In my case the drive was descibed at "dynamic". I changed that to "basic" under action. I then clicked the body of the window which contains the drive info, then right click and either format or pertition, choose a letter for your drive and you're away. Hope this helps
Chris