Do you have Revo Uninstaller installed on my system? If so, is there an avast icon. If there is one right click it and click uninstall and after that select advance, it will search for any avast related folders and files, select all, and click next, and it will uninstall it for you. It may open up the Avast uninstall dialog box, if it doesn't just allow Revo Uninstaller Utility to force uninstall Avast for you. When the uninstall finishes, providing it opens up via Avast uninstall dialog box it will ask you to restart, don't click restart, let Revo force uninstall Avast for you then click finish and restart your computer.
After that use avastuninstaller utility and Rejzors tool