I don't know if I'm set to scan archives or not. How do I tel?
If you're using the Pro (or Trial) version of avast:
Right click the task (Screen Saver) > Properties > browse the settings for 'archives'
If you're using the Home version of avast:
Control Panel > Video > Screen saver tab > avast screen saver > Settings (or Customize) > browse the settings for 'archives'
Hope this help