This theories include Microsoft Updates (today we have some ones), Windows Defender updates, etc.
Other theories say that windows startup which, for sure, does not follow a strict order, need to be tweaked in some way and use Startup Delayer. This tool manage the execution of programs that are automatically started by the operating system at logon time. Instead of executing many programs at once (causing your OS to spit and sputter and attack your hard drive), StartRight will give the OS time to execute the program before running the next program. The OS should become much more responsive almost imediately after logon.
Remember that since avast! version 4.7.807 the Standard Shield has a feature called do not scan system libraries (by default on) that dramatically decrease the number of files scanned during computer boot.