My parents just asked me to do a quick check of the home-security solutions for their PCs, as they’re having some issues with latest one they purchased. I took a quick look, and from the reviews I’ve seen, Norton 360 seems a good choice.
I also remembered that I’d seen a small USB device with an embedded Linux processor, running firewall software, so went searching for that. I found the Yoggie. It comes in 2 versions - one for connecting to a single laptop over USB (and it routes all traffic that hits your PC through the device before allowing it to get to you), and another (Yoggi Gatekeeper SOHO), that has 2 ethernet connections - so that you can install it as a bump in the line between your internet connection, and your local network.
You could build the same sort of protection into an old standalone PC and create a similar solution for next-to-nothing, but the simplicity of this solution (and the fact that someone else takes care of ensuring it’s up to date) looks like good value for money.
From the reviews I’ve seen, it looks good, if a little expensive at $250 purchase, plus an additional $69/year subscription (for the SOHO version).