Anyway, thought someone might like to know the silent install switches and AutoIt script for installing the registration key (Yes you need to register even though it's free. Not bad though). You need to run avast once installed then run this script to register it.
Silent switches:
CODE
Setup.exe /VERYSILENT /NORESTART /SP-
AutoIt Registration Script (replace the X's with your key):
CODE
WinWait("Registration")
WinActivate("Registration")
Send("XXXXXXXXXXXXXXXXXX-XXXXXXXX {ENTER}")
WinWait("avast! - simple user interface")
WinClose("avast! - simple user interface")
WinClose("avast! Simple User Interface")
WinActivate("Registration")
Send("XXXXXXXXXXXXXXXXXX-XXXXXXXX {ENTER}")
WinWait("avast! - simple user interface")
WinClose("avast! - simple user interface")
WinClose("avast! Simple User Interface")
Hope this helps someone.