Even the Avast Forum topic notification ended up in the spam folder. Too many things are going there that shouldn't.
Thanks for your help and suggestion. I may just be missing it, but I can't see the Avast Help topics that you posted an image of. There is no "help" button on my Avast control panel.
Secondly, I'm not sure what "the main page" is - "On the main page, it is possible to set the scan sensitivity as Low, Medium or High." My main page of Avast 7 shows
Summary
Scan computer
Real-time shields
Firewall
Additional Protection
Maintenance
Market
Thanks and apologies if I'm just not looking closely enough.