If the free version comes with the command line scanner, you could
create a batch file and schedule it with MS Task Scheduler (Control
Panel, Scheduled Tasks). Here's a sample batch file. Adjust parameters
to your liking. The example will scan all local hard drives, scan
inside archives and delete viruses found. Run ashCmd.exe /? for help.
@echo off
rem VSCAN.BAT - runs Avast command line virus scanner
rem
rem Place in Avast program directory.
rem
