I'm having issues with accessing Steam from my USB External Hard Drive on my Windows 10 computer and upon disconnecting and reconnecting the external drive and attempting to access it the green progress bar at the top of the My PC windows gets to about 95% then crawls to a halt and makes no progress so i'm wondering if it's finally starting to fail. And whether i should take my computer and external drive to a computer repair shop and get them to transfer all the files on it over to my computer's internal drive before the external drive fails completely.
I'd say that sounds like a yes
If you have a Linux LiveDVD laying somewhere around, test the drive using that. You should get a much more specific and helpful error if there's something wrong with it. Although the Event Viewer MAY already have information you need. Try that first.
Could be a USB connection issue, If it does get knocked about too much then the soldering on the USB socket can bend,twist and snap off.
If you don't mind taking it to bits, it's really just a typical HDD with adaptors on it and you can install the external HDD like any other HDD into your PC. This is often a one way thing because it requires to snap off the plastic shell.
IF you're gonna use it as a internal HDD, you should just get a HDD that's meant to be internal as external HDD do not perform as well and don't support features like Self-Monitoring, Analysis, and Reporting Technology (SMART).