Avast used to have BartCD in the pass which is a rescue disk and it not free, Avast already have Boot-Time Scan built into their AV software so is not really required to have a rescue disk as a standalone version any more. Maybe Avast might offer a free AV rescue disk in the future similar to BartCD & Comodo Rescue Disk (CRD) etc etc, this option is totally up to Avast to provide a free standalone rescue disk maybe yes or maybe no.