Indeed I did turn it off in the tools tab as -midnight indicated.
If the tools tab has the option to turn it off then surely the onus is on avast to make that action work, not for me to have to go around deleting system files?
Your system, your choice entirely, but what you have tried clearly hasn't worked - as an avast user like yourself (not an avast employee) I offered a way to get rid of it completely if you don't want it.
You aren't having to delete system files you're simply asking avast via the Windows Control Panel Change option to remove the avast module, no system files involved.