baixe a ferramenta de desinstalação

https://dl.dropbox.com/u/73555776/aswclear.JPG

http://files.avast.com/iavs5x/aswclear.exe

pressione f8 para entrar em modo de segurança repetidamente
e siga estes passos

http://www.avast.com/pt-br/faq.php?article=AVKB10

locais de download 8.0.1497
http://files.avast.com/iavs5x/avast_free_antivirus_setup.exe
http://files.avast.com/iavs5x/avast_pro_antivirus_setup.exe
http://files.avast.com/iavs5x/avast_internet_security_setup.exe
http://files.avast.com/iavs5x/avast_premier_antivirus_setup.exe