A link to an article in the April 14, 2004 Village Voice led eventually to this page with trial offers and discounts on various AV products:
Use Up-to-Date Antivirus Software (for Windows XP)
To work through Microsoft's advice on firewall protection, Windows updates, and antivirus software for yourself (and other operating systems), start here:
Microsoft Protect Your PC
and choose the Detailed Steps option when you get to the second screen.