I downloaded SeaTools for Windows and SeaTools Bootable. The Windows
tool notified me of failure but couldn't fix the errors causing the
fail. It suggested creating and using a SeaTools Bootable USB disk
which is capable of fixing errors. I ran the same tests with the
bootable USB and all tests passed after their scan fix. I want to
thank you VanguardLH and all those who replied with advice.

No mention in your opening post as to the frequency of the reported bad
block in the Event Viewer. Was the frequency so often that now after
using SeaTools that you are sure the error cause has gone away?

I had another bad block experience about 3 months ago. I had to run
chkdsk 4 times to get rid of all faults. If things get worse I'll
replace my HD. Looks like I can get a new 500 GB SATA for $30 at
Walmart. But restoring Windows 10 Home authentication from my original
Windows 8.0 key might be difficult.