Here is an excellent article about what each of the Anti programs does and which do a better job. Written in english - not geek speak.
http://www.wired.com/news/infostructure/0,1377,63978,00.html?tw=wn_tophead_4
The article addresses spyware, not viruses. I was referring to trojan horse programs. Back Orifice was a trojan horse program, as was subseven. It's those types of programs that are of concern because they're not used to push advertisements to the computer, but to remotely control the computer as a 'zombie' so it can be used in an attack against other computers. Personally, the combination I use is Norton Anti-virus 2003 (less junk than '04), Ad-aware (free) and Spybot (also free). In addition, I exclusively use Mozilla, including its built-in email application. I stay virus and spyware free on both my home and work PC. It's really not all that tough to keep things running smoothely, it's just that most folks don't know the few things necessary to keep it that way.