Re: Secure boot
Fixing the UEFI BIOS by disabling secure boot (setting it to "Other OS") worked, BUT:
That still left me with two notices that appeared at boot, both of which I had to click through. One said, <Asus Setup C:\Users\******\AppData\Local\Temp\211540Log.iniis lost> and the other was identical except that it referenced 211241Log.iniis lost>.
More Googling suggested entering Task Scheduler and deleting or disabling the i-21 entries. I did so and disabled them both; upon reboot both notices were gone and did not return. Whee! Note I went to Control Panel\Administrative Tools\Task Scheduler, not Task Manager.