CA Internet Security Suite 2007
Here's another special offer that I just found when looking for anti-virus/spyware tools for my family's computers - you won't find this on their web site without a special URL: http://home3.ca.com/microsoft/
That URL gets you anti-virus, spyware, firewall and anti-spam for 3 PC's for $30. $10 a computer is a pretty good deal.
Now, there are some caveats.
I had to severely downgrade the default protection on the firewall because it disables all script - so all the kids web sites like disney.com won't work. The wife couldnt shop on gap.com and others (though that may not be a bad thing)
It wouldn't allow us to share a network printer - and their tech support answer of "add all ip's on your network to the exclude list one-by-one" was very disappointing. (can you imagine your mom getting that response)
I didn't even try the anti-spam - kids don't have email and wife and I use Spambayes which we love.
We're still tweaking the settings after a few days to get everything to work as it needs to, but the firewall was the biggest problem to find the right balance. Overall, I'd recommend it - but I doubt that you can run with default settings.