SUCCESS!
I repeated the SFC /SCANNOW with the same ineffective result, so I tried yet another scanning program to clean the registry, etc. (SpeedMaxPC), and although it cleaned a lot of stuff, I still couldn't get MS Update to work. Then I explored the link given by ICit2lol about Windows Update Service Not Running (but it is), and determined that my Intel Rapid Sotrage Technology (RST)
drivers had to be updated to work with a drive > 1TB. Quick easy install with a couple of reboots, and now all is fine!
Thanks to everyone on this great forum! I literally couldn't have done it without all of your help!
Stan