I have had this backup drive for several years. It has always shown up as an H drive. For a couple of weeks it was not showing up on my drive list at all. Today it showed up as the E drive, but now comes up with an error message that says "The disc in drive E is not formatted - Do you want to reformat now?" I'm betting this is a bad omen. I have 5 years of photographs on this drive. Is there anything I can do to get the files off this unit before it dies?
There are various programs available online, more windows based than any other OS. Most of them have a free trial to verify your data is there before purchasing a license. The alternative option is professional data recovery services.