First, let me confess the question title is not precise: I apologize, but I didn't find a short way to describe the real problem.
My External drive works good, it contains a lot of file and I can access them easily. But to access it I first have to unplug it, then turn it on and finally plug it in again: if I turn it on whit USB cable plugged in Windows doesn't recognize it at all.
It's not a tragedy, but I'd like to fix this to get a more comfortable access to my files :-)
Using Windows 10, but thiss happened even on Windows 7 and 8.0 and 8.1