Download the REMOVAL TOOL for your current Anti Virus Program by following the Guide offered here:
How do I remove old third-party antivirus software before installing avast!?
[b]https://support.avast.com/index.php?languageid=1&group=eng&_m=knowledgebase&_a=viewarticle&kbarticleid=574[/b]
( The removal tool for avast! Antivirus (should you ever need it) : http://files.avast.com/files/eng/aswclear6.exe)