Leo, thank you for your prompt response. I tried what I could in the article attached to your email, but still got the same error message when trying to install DOpus (version 11) aftwerward. The installer is not corrupted; in fact I've used it before when I've had to reinstall the program. The permissions in Public Desktop were correct. I also checked Process Monitor but was unable to find any entries related to the DOpus installer. I was unable to delete the Install Shield folder, and there was no sub-folder in the Install Shield Installation Information folder whose name ended with BF50D. I did empty the Temp folder. There was no record of my anti-virus program (Bitdefender) having blocked the DOpus installer in the past 3 days.
I should also add that I took my laptop to a local computer shop last Friday (12/29), where Windows 10 was reinstalled and the computer's firmware updated. All my other programs were restored successfully and function properly, but they mentioned not being able to get DOpus to work.
DOpus is far and away the best file manager I've ever used, and I would really like to get it back. Is there anything else you can suggest?