Followed your instructions.

Avast installed successfully - and the setup process told me I have 30 days of free protection too.

A “startup scan” began running soon after, something that wasn’t happening before.

I have a feeling this is a sign that the installation FINALLY was a success. [update: It WAS a success. Everything’s in working order]

While typing this, the startup scan completed. No threats found.

Thank you SO MUCH for your help, both of you. This thread may be closed now. But if I have further problems, or any questions, I won’t hesitate to ask.

Edit: Registered Avast soon after as well. Now I have a whole YEAR.

;D