Thanks! That's the most helpful thing I've been told. It helps me to realize that I'm not crazy.
My frustration is that the nvidia drivers from Additional Drivers did, at one time, work for me. That was a number of years ago. I think I was running Mint at the time (although I don't think Mint had anything to do with the drivers working). And there were two different drivers offered - a 304.??? version and a (I think) 179.??? version.
Now only the 304 version is offered. It's hard for me to believe that a driver offered by nvidia would loose compatibility with the card it's designed for..!? I tend to believe it's some step in the install script that has been changed.
What happens is that after I install the driver from Additional Drivers and reboot, the screen locks up at the nvidia logo. I never get to the sign-in screen.
I have read somewhere that you have to reboot in nomodeset.? I think the point being made was that the nvidia drivers do not load correctly from grub, and you have to get past the sign-in screen for them to load. If this were true, I would think the install script would be set up this way. But, I have to confess, I have not checked this grub setting during reboot - I get the frozen screen and go back and remove the nvidia drivers.
Anyway, I'm going to read all the links you sent, but my suspicion is that the problem is in some configuration setting during reboot and not in the drivers themselves.
Thanks, Jim
Edit from ouroumov:
In order to close this thread, I'm linking the solution posted by @Jim007 in the following thread and then marking this last post as solution.