Even though the original post date was a few years back, this info is still valid and was very helpful to me in fixing a problem with Avast installs.
A big "Thank You" to Sonic & LaptoniC!!
QUOTE (LaptoniC @ Nov 26 2005, 05:30 PM)

If you search the forum you would find the post.Anyway,create Admin.ini file where your setup resides with below content.
QUOTE (Admin.ini)
[Admin]
SilentInstallation=1
Serial=YourFree-Key
Install your AV with below command.
QUOTE (install.cmd)
@echo off
cmdow @ /HID
start /wait yoursetup.exe
Echo [Splash] >>"%PROGRAMFILES%\Alwil Software\Avast4\DATA\avast4.ini"
Echo KeyUsage=1 >>"%PROGRAMFILES%\Alwil Software\Avast4\DATA\avast4.ini"
Exit