What I mean with "optional" processes is anything that is not a "must". Many users tend to use some method of automatic startup for several different things, so they automatically start together with Windows.
Some examples may be quicktime, flash autoupdate, printer tools, theme tools, tools to enhance office performance (for LibreOffice, OpenOffice, MS-Office...), RAM tools, autodefrag tools, monitoring tools...
Some of those might show some icon on the tray area. Some might be listed in the Task Manager, and there are several places to find the "autostart" tools, depending on the method used to start them.
My point is that there might be something conflicting the setup of Avast, or at least making it so slow that it seems that is not responding.