I see that when I go to scan and scan settings, I cannot change any of the Settings as how I would like to set them to do a full system scan as this is a read only window.
When did this become a read only window? I ask this because the previous free version of avast which was 5.0.545 I could go into scan settings and set the scan settings as I wanted to make sure I had maximum protection against viruses and spyware.
It has been that way for some time and the reason is that they are pre-defined scans, and as the comment at the top of the pre-defined scans settings says, see image. If you want to change the main elements of a pre-defined scan create a custom one.