free antivirus

hi folks,
if you are searching for a free antivirus, from my personal experience, i would recommend avast.
as it is free and provides protection to your system fully. no doubt,it may not provide fully protection from internet. but it is helpful in most cases. and the
1. most recent version provides sandbox feature.
suspicious programs runs in sandbox so that  your files or OS will not be harmed,
2. it provides a add-on for browsers which shows, whether the site is harmful if you visit it.
3. the free version provides 7 shields to protect your system. overall it is a good antivirus for normal users.
4. you can get a registration key valid for 1 year by registering on avast.com (it is for free version only).

here is the link to get avast.
download avast free version

and link to get a registration code
Register here
if you believe there is any other product better than avast please be kind to leave a comment.