I am usiing AVAST Free, after having the paid version registered and expired.
Now I cannot register FREE because my email is already established.
So I have to keep uninstalling & reinstalling !
https://my.avast.com
Delete the device from your account.
Delete avast completely from your system (including using the uninstall tool)
Reboot
Run CCleaner and have it not only clear/remove all temporally files,
but also keep running the registry scanner/cleaner until nothing is found anymore.
Reboot
Install the latest avast (free) version and register it.
All this was completely un-necessary. I ignored the register prompts in AVAST, and went to the Website and used the “Register” link there.