I think it may be better just to perform a clean install, download and run the avast removal tool http://files.avast.com/iavs9x/avastclear.exe when you click to run the tool it will ask to boot to safe mode, accept and it will reboot and when the tool opens choose from the dropdown list the version of avast you need to clear and run.

“Note” download a fresh copy of avast and save first if you haven’t saved previously http://forum.avast.com/index.php?topic=136785.msg1000473 then download and run the removal tool.