hi kokolovich,
Just so you know, a PUP (
Possibly
Unwanted
Program) scan is not set to run out-of-the-box because some users don't understand what a PUP is. Avast! developers have set it to not run to minimize complaints against their program but have also offered the option to scan such for those who do know what a PUP is. Problem is, many users may well have a program or two they like, but once avast! is set to scan PUP's it doesn't like it and may well then remove it from their system.
Definition of what a PUP is here: (Includes all other malware definitions, so you will know a little better what you are getting into):
http://en.wikipedia.org/wiki/Malware#Grayware Grayware is also know(n) as PUP.
For the average user, the default settings out-of-the-box are best left as they are; any missed detections that occur, the majority of the time, are not because avast! was not set to the maximum settings but because the virii malware is
unknown to avast!
You may be looking at possibly a few false positive detections on known clean (not infected) files running at maximum settings, so... Never delete a file as it may well be clean under these conditions. Once a file is deleted, it is gone forever. Delete a Windows file (not an application file) and you break Windows and that may be a false positive detection (FP) so now you've got a problem where there was not one before. Think (or ask here) before you do anything.
[EDIT:] Malwarebytes Pro (Paid for or 30-day trial version) monitors your web connections and blocks those it considers to be harmful. The free version does not have this type of protection.
You can safely run both Malwarebytes Pro (or free) and avast! together; they are compatible. No adverse impact on your system under normal use.