The Best Antivirus Software

kaspersky AntiVirus

Award-winning antivirus software which protects your PC from viruses, Trojans, spyware, rootkits and other malicious programs. Reactive detection methods are combined with proactive technologies to provide balanced and effective security, while automatic updates ensure uninterrupted protection and peace of mind.
http://www.kaspersky.com/kaspersky_anti-virus

Free AVG Anti-Virus

GRISOFT announced that AVG Anti-Virus Free is the number one downloaded program on all of CNET Download.com. Additionally, AVG Anti-Virus Free is the first most popular and Anti-Virus Pro is the third most popular antivirus based on Editor’s Choice. CNET Download.com is a well-referenced site and is part of CNET Networks, an internationally established online publication and host to technology news and reviews.
http://free.grisoft.com/