well I use Norton takes a little getting used to, 40 bucks isn't that bad per year. I used to use Mcfee but really disliked it as it kept telling me over and over that it was not up to date even 2 seconds after I ran the lastest updates. but I think 40 is the general price for anti-virus software.

Norton AntiVirus 2009 - Windows

but that's all I've dealt with, main thing is that you need something, and set your computer to auto update everything each day