firewall not working after initial upgrade install

[jssjrob]

I upgraded from the free version and upon restart the blue screen of death appeared. I restarted in safe mode with "use last good configuration", started OK but the firewall will not start?? I'm not tech savvy, so please keep any responces easy enough for a block head to understand 

[JuninhoSlo]

I upgraded from the free version and upon restart the blue screen of death appeared. I restarted in safe mode with "use last good configuration", started OK but the firewall will not start?? I'm not tech savvy, so please keep any responces easy enough for a block head to understand 

Try repair AIS. Don,t forget restart your PC when you done.

[jssjrob]

OK,
 Where do I find the AIS repair?

[Pondus]

avast repair and reboot

For a repair of avast. Windows, Add Remove programs, select 'avast! Anti-Virus,' click the Change/Remove button from the pop-up window, scroll down to Repair, click next and follow.