Avast antivirus is one of the top leading antivirus and it is available for free download.You will get a fully functional 30 day trial version of avast if you download directly from their website.To activate it for one year you need to register with them.Once registered you will get your Serial license key into your mailbox.Here are some of the features of Avast 6 Home Addition Antivirus
Avast Sandbox: Using Avast Sandbox you can run programs suspected for viruses in an isolated envirnoment so even if they contain any virus your computer will be safe.
Website Block: Website Block technology allows you block websites that should not be opened by family members.
Webrep: It allows you to rate websites in your browser.
Open Official Avast Registration Page by Clicking here
Enter the details in form and you will recieve your License serial key within 24 hours at your email id.