I have uninstalled Avast as required. However, I had a problem with Windows 7 update which made my mouse very jerky on the screen.After much investigation on the web, I went for a roll back to the previous working system (i.e. pre the update) and that completely banjaxed the computer - there was a problem with various api-ms-downlevel-xxxxxxx.dll files as missing. As that also affected Avast, I thought best to uninstall it with the Avast uninstaller but it failed to completely uninstall. What was left, I don't know.
Having remedied the Windows 7 problem (by running ms scf, which probably would have solved the entire problem if I had known about it in the initial stages), I have been unable to install Avast, so after numerous attempts, I decided to go with a different Antivirus software (there was no problem installing it) which is working fine but I will never know if it is better than Avast.
I should add that Avast let a ransomware through back in December last year which left me without a computer over the New Year (not to mention the cost of getting it removed). Since then, I installed Linux as dual boot which has proved very useful during this lastest fiasco as I was able to boot into Linux and use the internet, download various recovery programs, move them to my Windows desktop and then go back to Windows and run them.
Long live the dual boot machine! So, sorry Avast, after over 10 years of using you, I have now fled the nest.