Did you receive any message about Avast failing? Or when the installation finished, did you see any “successful installation” or similar?

Have you rebooted after installing Avast?

Do you have or HAD any other security tool (firewall, anti-virus/spyware/phishing/…)?

About your ISP installing something, if you have no idea, then who? :slight_smile: I guess you can only ask them (the ISP).

Do you have Avast listed in the Control Panel → “Add/Remove Programs”?

What exact OS do you have (edition, version, SP, 32/64bits)?