@rwebert
You said the computer will not recognize the drive -- but that does not provide us any useful details.
To see if Windows can read the drive, do the following:
1) In the search area, enter "create and format" and select the Create and Format option. That will open the Drive Management window
2) Scroll down through the drives listed in the window until you see your external drive
3) If it is not listed, that means the BIOS can not see the drive and thus, Windows will not be able to see it either. That means a hardware issue with the drive.
4) If it is listed then look a the details. If it shows the partition as RAW, that means the drive has become unformatted and Windows will not be able to read it.
5) If it shows the drive as formatted but there is no drive letter, then use the option to assign a drive letter. After that, Windows will be able to see the drive and you will be able to access it.
I am a volunteer and I do not work for, nor represent, HP