Kaspersky Anti-virus is one of the best anti virus solutions available for PC users. Kaspersky recently released 2009 version of the security software, to popularize use of Kaspersky they are giving a free trail key that is valid for six months.
It protects the operating system from malware, adware, splyware. 2009 version comes in two flavors Kaspersky Internet Security priced at $59.95 and Kaspersky Anti Virus 2009 priced at $39.95. You can use Internet Security 2009 for six months with this trial key.