I believe I installed a "free" copy of this once and it gave me nothing but headaches. I have an AV program now that is actually free and works, and I got the reccomendation from CNet.com. They are a great resourse for information about things like this.
Yep, I just go to download.com and find the one for free that is downloaded the most. McAfee always seems to take up so much memory, and never seems to find the viruses that I have.