I use Avast!. It's relatively lightweight, doesn't BSOD systems like AVG has, completely free and with no popups whatsoever. I think it still supports old OS's, tho since you mentioned Windows Firewall that's obviously not an issue.
Windows Firewall is adequate, though hardly very good. If you know what you're doing you can get away with it, but if your partner/kids/some neighbours' dog is using your machine you'd want something that actually does it's job (read:anything but ZoneAlarm, I recommend Kerio).
Windows Firewall is adequate, though hardly very good. If you know what you're doing you can get away with it, but if your partner/kids/some neighbours' dog is using your machine you'd want something that actually does it's job (read:anything but ZoneAlarm, I recommend Kerio).