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#11
Did you deleted ALL partitions till you get one and only one unallocated space?
How To Fix Error 0x80300024 When Reinstalling Windows 10 - YouTube
Thank you for the YouTube link (which is very good), and especially for your "ALL partitions" prompt. Although I had removed the old system drive and my data drive, I had left in place a drive with nothing on it. Following your prompt, I removed that drive also, and then the Windows installation software functioned correctly. Problem solved!
Thank you so much for your solution (and also to NavyLCDR for his help earlier.)