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.