The best virus software is software that spends it’s time focusing on what it does best, protecting you from bugs. You should avoid virus software that is bundled with malware protection, link scanning, internet fraud protection, and any of the other things they tend to bundle into them anymore. Having all of those bundled in one tends to slow down your system, and makes for a crabby computer user. At the moment the best free software I can recommend is Avast, it’s the one that I personally use. Always be sure to have another program that also protects you from malware, such as Adaware, or Spybot, to make sure that you are protected on all fronts.