Sometimes it’s not possible to uninstall avast! the standard way, using the Windows Control Panel. In this case, you can use uninstallation utility aswClear.
Disclaimer: Any third party tools are to be used at your own risk. Kaspersky Lab ZAO will not be held liable for any damage and/or loss of data that may result from running these tools. We are unable to provide support for the use of 3rd Party tools.