Important Tips
* Watch Out -- Do not buy or download any antivirus software without checking this list first: The 69 Worst Antivirus Scanners, Mary Landesman, antivirus.about.com, September 15, 2008.
* Just One, Not Two -- Never use two anti-virus products at the same time. Completely uninstall one before installing another. Use the vendor's uninstall utility or if not available, use the Windows XP add/remove software tool in the control panel.
* Patches & Updates -- Anti-virus software is only as effective as its most recent update because it is inherently reactive treating "known" threats. So when you install anti-virus software, go to the vendor's web site and update the program and virus definitions immediately and then turn on the auto update feature (if it has one). If you want to be ready for the next big bad thing before your anti-virus signatures can be updated, consider Zero-Day Protection.
* Get Online Protection Too -- Consider using an Internet service provider or email service that includes server side anti-virus and spam email filtering as a second layer of defense. If possible, use different anti-virus software on your home computer than your ISP or service uses on their servers.
* Consider a Gateway -- A Broadband Gateway product between your modem and network can screen out viruses before they hit your computer(s).
* Spyware & Trojan Horses -- Some anti-virus software products now include anti-spyware and some anti-spyware products have added anti-virus. In addition, some of these products include anti-trojan, anti-worm and other anti-malware features. Before relying on a single security product, carefully review the vendor's list of features and study comparative test results if available. See Editorial - Do you really need a spyware scanner? Gizmo Richards' Support Alert Newsletter, April 17, 2008. Also see our Security Suite, Anti-Spyware, Anti-Trojan and Zero-Day Protection pages.
* Prices -- See our custom Anti-Virus Price List powered by Amazon.com
Source: http://www.firewallguide.com