the real question here now is:
did you change the FILE or a setting in Avast itself?
if its a setting then you have to look in the GUI for it
since you say you reinstalled avast i have to logically conclude that its your setting that is kept in registry and not a file that you changed
another logical assumption is that since you didnt know you have to disable the avast self defense you could never have replaced the file in the first place if you actually changed the file, hence my first question
