Like AVG, ZoneAlarm comes in several flavors of paid versions, but again, it's all extra bells and whistles you may never need or use. The free version has been more than adequate for my home modem connection. You can also test its reliability (as well as that of any firewall) by running Steve Gibson's ShieldsUP!.
Finally, we come to Microsoft Outlook and Outlook Express. While Outlook and its variants are solid email clients with a lot of excellent features, let's face it: it has a very poor reputation that has led to several viruses being tagged "OTD's," or "Outlook-Transmitted Diseases," by the security community. It's intended as tongue-in-cheek humor, but unfortunately there's truth behind it. Unless you are consistently updating Outlook alongside Windows, chances are you're going to fall behind on patches and become vulnerable.
Fortunately there are several free mail clients out there. If you're running Mozilla, Opera, or Netscape as your browser of choice, you've already got email capability built in. Jump in and tinker, you may be surprised at what it can do. My personal favorite email client is Eudora, and I wish like hell they'd port it to Linux. Windows and Mac users can download it for free at eudora.com. Simple, powerful, and elegant. Great stuff.
With all this information available, there really is no excuse for becoming infected or spreading viruses other than plain user ignorance. My school's network receives several per week, and I am constantly emailing people to teach them how to prevent the spread of viruses. While no software will ever become 100% resistant to viruses, proper use and maintenance and user education can go a long way to stopping the spread of these malicious viruses.