RZPogi
3
When I installed avast on my windows 8.1 systems, windows and/or avast automatically deactivated windows defender. Windows Firewall is not affected.
Windows 8/8.1 automatically detects if a legitimate antivirus program is installed and deactivates windows defender if it has found one.
Since you are using avast free, you don’t need to and shouldn’t deactivate windows firewall.