I’d recommend running a clean install:
1.Download your version of avast and the avastclear tool - save them to the desktop:
Avast Free Antivirus
Avast Pro Antivirus
Avast Internet Security
Avast Premier
Download Avast Clear Tool
- Uninstall Avast from Control Panel (if possible) and reboot.
- Uninstall in safe mode using Avastclear. [Running Avastclear is normal mode will give a prompt to go into Safe Mode]
- Install the version you downloaded.
- Reboot.
Paid: If you have a paid license, insert the license key/activation code after the reboot at stage 6.