Let me put it this way ... On a computer running Windows it is cheaper to buy an antivirus then it is to remove a virus.

Shy away from McAfee, it is garbage!

Why would any company give you free software? In my opinion they give you free software because it is not good enough for them to be able to sell it.

The main difference between paid software and free software ... is that the vast majority of free software is reactive ... not proactive.

You don't need an antivirus for UNIX based systems (ie. MAC OSX)