One of the software I recommend to most of my friends is Avast anti virus program. It is a very free program and you can get 1-year license just by giving them you email. I not once have any spam from them. If you buy a computer in Thailand many shops installs illegal version of anti virus programs, before they do ask them to install the Avast program.

About Avast

avast! antivirus software provides complete virus protection for your computer. Antivirus engine is complemented by anti-spyware, firewall and antispam modules to protect you against phishing schemes, identity theft and internet-distributed web viruses. Automatic updates for greater user convenience and safety. Top user ratings among free antivirus software.

If you have any questions please feel free to ask in the forum.

Free Anti virus Download