Not knowing your OS. Try (XP) control panel…click add/remove…double click “avast”…scroll to select uninstall. (Vista and Win7) control panel…uninstall…double click “avast” scroll to select. Personally I find the uninstall utility to work better. Just remember the location you downloaded it to. Vista and Win7 check the download folder. It is always better to uninstall using “safe mode”. Don’t forget to re-boot. 