Then maybe you should go to Avast Support and ask them.
That's what I just did. I got within a short time this completely unrelated answer:
"This is the best way to use avast! to remove any infection:
1) Update the virus database
2) Schedule boot-time scan.
3) Restart your computer again. The boot-time scan will start - let it finish and move all the viruses found to the chest.
Now you should be virus-free. But if the virus is still present on your computer, try to use some removal tools, like: ..."
Given that fact that the free Avast version is already very good and getting great reviews everywhere I wonder why anyone would upgrade to a paid version if you are getting nagged there into buying or installing more stuff all the time, too.