Doesn't detect MyWebSearch or AdvancedVirus Protect

What’s the point. Avast says I have a totally clean system, when other virus scanners find these and other trojans and other spybot cookies.

Malwarebytes’ Anti-Malware (MBAM) is a perfect companion to avast!

Download MBAM then update it then run Quick scan and have it remove what it finds:
http://www.malwarebytes.org/mbam.php

A reboot may be necessary to remove locked files.

What other scanners as there are many rogue programs masquerading as security software ?

Spybot cookies ???, a waste of processing effort. Don’t worry about reported tracking cookies they are a minor issue and not one of security, allow SAS to deal with them though. - See http://en.wikipedia.org/wiki/HTTP_cookie.