CLAMAV may not be your choice, but it works and isn't full of other malware as other so-called "free" AV apps are. I am helping folks all of the time who are infected by free security software that leads to nothing but headaches.
Not saying your link is bad, but I know that CLAMAV is clean, thus the recommendation. BTW, it works great on my system (W2K3). No bells and whistles, just gets the job done.