Boot-time Scan

I had a virus that would not let me run Avast (Home) even in Safe Mode. I couldn’t even run IE or Explorer. Is there a way to run it on boot up from a flash drive or CD?

I suggest scanning with DrWeb CureIT! instead of trying to run avast for DOS.
You can schedule avast at boot time running:
C:\Program Files\ALWIL Software\Avast4\sched.exe /A:“*” /archives