Once downloaded, run Live Update until it returns 'No Updates Available' (or similar wording), then reboot your computer. This will give you the latest version.
Wait a couple of minutes between updates to allow them to install.
Just read your reply on how to install Comcast Anti-virus, but what I would like to know is how to un-install it, as I don't remember downloading it anyway. Don't recall seeing it in my Control Panel, but I started getting updates notices was how I knew it was on my computer. I'm not saying there's anything wrong with the program but I already have a Anti-virus program and don't want more that one.