Welcome to the forum.
Instructions to successfully install avast! 6: You can also download these instructions from:
http://goo.gl/4IKlO01. Download the product avast!6 Free:
http://files.avast.com/iavs5x/setup_av_free.exe02. 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!?
https://support.avast.com/index.php?languageid=1&group=eng&_m=knowledgebase&_a=viewarticle&kbarticleid=574 ( The removal tool for avast! Antivirus (should you ever need it) :
http://files.avast.com/files/eng/aswclear6.exe)
03. Once these 2 programs are saved to your computer in a folder that you can locate or,
to the desktop and, you can easily identify these 2 files, DISCONNECT FROM THE INTERNET
04. Go to the Control Panel > Select add/remove > (Programs and Features in Windows 7)
select your current antivirus program and select uninstall. (Allow it to uninstall all features of the program)
05. Reboot your system.
06. Run the removal tool for your old Anti Virus Program saved in step #2
07. When the tool finishes running, again Reboot your system.
08. Install avast!6 Free by running the program downloaded in step #1
09. Shut down your system -- Reconnect to the internet -- Start your computer.
10. Avast!6 Free will now be installed and will update it's virus database.
11. Register your new avast!6 Free product by selecting the Register Now button.
If you need more help, get it from here:
http://www.avast.com/registration-free-antivirus.php