As ExCyber mentioned, Zone Alarm is a great choice. If you're just looking for something simple like me then it's probably the best choice out there. It doesn't let you customize it to what ports get what access etc. So if you're looking for advanced features I'd skip it and be ready to shell out some cash for one. It's very, very easy to use. I've only had a few problems with it which are usually circumvented by disabling ZA while you run whatever program is incompatible with it (so far only a handful of multiplayer games). Great, free, simple protection for an "always on" type of internet connection.