Winpooch. Its a program that monitors what programs are trying to do. It can be setup to block programs from connecting to the internet, making changes in system folders, etc. Out of the box its a bad 'firewall' because it will let everything connect to the internet. By changing the rule to 'block everything' and then adding exceptions, you can create a lean and mean firewall. I've posted a guide to configuring Winpooch as a firewall here. The primary drawback with it, is it doesnt have an option to run as a service, though i hear that's planned. I do reccomend ZoneAlarm (particularly Security Suite) over the other commercial firewalls though.