Most Internet Providers provide free antivirus and firewall software to their customers!

I find that a lot of people don't take advantage of this. Companies like Qwest and Cox Communications (and others!) partner with software companies to bring free security software to their customers.

In the Phoenix, Arizona area:

Cox Communications - McAfee Internet Security and Antivirus Software

Qwest - Norton Internet Security & Antivirus Software
(they may try to sell you an upgrade package, but the added cost is simply more online storage and will not provide more security than the free package)

Microsoft's new FREE Antivirus Software

Microsoft Security Essentials provides real-time protection for your home PC that guards against viruses, spyware, and other malicious software.

Microsoft Security Essentials is a free* download from Microsoft that is simple to install, easy to use, and always kept up to date so you can be assured your PC is protected by the latest technology. It’s easy to tell if your PC is secure — when you’re green, you’re good. It’s that simple.

Microsoft Security Essentials runs quietly and efficiently in the background so that you are free to use your Windows-based PC the way you want—without interruptions or long computer wait times.