1. Avg anti-virus :- After using many anti-virus, I found that Avg anti-virus is the best selection. It doesn't consume much memory , also fast in working and provide best security to the system. But you need to update it every day.other wise it will not be able to handle the threat of new viruses.this step is common in the case of every anit-virus.If you want to secure your pc from viruses.
There is a link for downloading this Avg Anti-virus.
download Avg anti-virus
follow the link and download will start in few seconds and trust on me this is best anti-virus as i have judged.