McAfee AntiVirus Plus 2010 with 3-User License for $19.99 shipped.  Here is a screenshot for your reference.  Alternatively, it is available at Amazon for the same price with free shipping on orders over $25.  This program shields PCs from viruses, spyware, and has a firewall to protect against network attacks.  It also features McAfee SiteAdvisor that warns about risky web sites before users visit them.  Most places have it for over $50.

Originally posted earlier, it has been slightly revised and this is just a friendly reminder.