The best anti virus program that is free seems to be AVG. AVG is a free anti virus program that does a great job at keeping itself up to date and keeping your computer protected from viruses.

It is recommended by several PC review websites including CNet. It is said to be one of the most downloaded free antivirus programs on www.download.com.

Follow up:

The Program can be free because it offers more features if you buy it. But it does a great job how it is. If you think you need extra computer protection from viruses feel free to support AVG at http://free.avg.com/.

If you are interested visit the download page here:

http://free.avg.com/download-avg-anti-virus-free-edition

AVG Free provides you with basic antivirus and antispyware protection for Windows and is available to download for free.

There are other antivirus programs that are very professional in how they work. NOD32 and Norton Antivirus seem to be at the top of the list but AVG beats them all in user satisfaction. Many antivirus programs will let you try them before you buy. So do some more research if you want to look beyond AVG. Feel free to comment about any antivirus program that works for you.