Top tips for not getting viruses:
DO NOT use Internet Exploder, use FireFox
DO NOT use Outlook Express, use Thunderbird
NEVER double-click a file with a .exe, .bat, .cmd or .vbs extension unless you can 100% verify the source of said file
USE the Windows firewall
Set your Windows theme to look "different". Then you won't be fooled by fake dialogue boxes
Buy a Mac
Use Linux
This laptop (hers), runs XP, with built-in firewall, has McAfee and a public IP address. It sits on the kitchen worktop, is never switched off, and has never had any virus problems.
You can get the best AV in the world, but there's only so much it can do in the face of naive (stupid?) users who click everything in sight.