Maybe my sarcasm detector if off, but aren't windows updates and Microsoft Security Essentials (a pretty good AV from what I hear, I wouldn't know as I run Linux) completely free?
I don't run Windows either but I read articles in which Microsoft plans to sell their anti-virus service, for example [1].
Moreover, even if these are presently free, in the context of this thread we should consider the experience of users over two decades of history of Windows and Office products!
I understand being wary of MS, I've used their products since the mid 1980s, (Switched over to Linux for everything but gaming about 10 years ago), but you do realize the article you referenced is from 2003?
