Bitdefender and Avira both also offer free versions, the former being my preference. As far as I can tell from a quick Google, Bitdefender's free version provides just as much protection as the paid version, just without all the bells and whistles that most people probably don't need.
Shame Kaspersky don't have a working business product. They are still in beta, and have been for the last couple of months with no sign of a launch. The beta doesn't work with the November update either.
I imagine this will be the problem with each new update as well, as they are notorious for being far behind the curve when to Windows version updates.