The questions that many of my clients ask continually is that of the effectiveness of free anti virus suites.
Again the primary source of the information was independent lab AV-Test.
Please refer to previous post of paid Anti Virus suites about what criteria were used to evaluate its usefulness: 3 categories included: protection, repair, usability.
Avast Free Antivirus and AVG Anti Virus Free Edition are on the top with Avira Free Anti Virus ,
Pc Tools Antivirus Free 2012 and Comodo Internet Security Premium. Microsoft Security Essentials
Please take under consideration that the anti virus programs are constantly reevaluated against new threats and their effectiveness might change. Safe practices for Inernet and e-mail are also very important as the part of safe computing.
For additional steps that you could take, please contact me.