I never found an antivirus program that I liked while I was using Windows. they all seemed either bloated (Norton) or kind of janky (most of the free ones). So you're on your own there. XD;
A software firewall really isn't necessary—it's just nice. If you have a NAT router (and almost everyone does these days. If you don't have one, you need one) you already have inbound protection. The only thing a software firewall does is provide you with outbound protection. That is, if you already have a virus or trojan on your computer, it'll potentially stop it from sending things like your keystrokes or spam from your computer.
The thing is, all the software firewall can do is alert you that a program—any program, even a safe one like your browser or IM app—is trying to access the internet. If you just mindlessly click "OK" to every application that asks for permission, you're likely allowing the virus access, which defeats the purpose.
That said, be sure that your router doesn't have UPnP enabled, or a bunch of holes opened up through port forwarding. A good way to test that is Shields Up!
The conventional wisdom for all of this is that, once you've gotten a virus of any kind, you're pretty much compromised and should reinstall Windows. Spyware in particular has gotten so malicious that it's almost impossible to get rid of it any other way. If you keep scripting off in your browser, don't go around to "weird" sites, and don't randomly download stuff, you'll probably be fine. Maybe.
A software firewall really isn't necessary—it's just nice. If you have a NAT router (and almost everyone does these days. If you don't have one, you need one) you already have inbound protection. The only thing a software firewall does is provide you with outbound protection. That is, if you already have a virus or trojan on your computer, it'll potentially stop it from sending things like your keystrokes or spam from your computer.
The thing is, all the software firewall can do is alert you that a program—any program, even a safe one like your browser or IM app—is trying to access the internet. If you just mindlessly click "OK" to every application that asks for permission, you're likely allowing the virus access, which defeats the purpose.
None. I like don't use any because I use a Mac. =p
avast and ZoneAlarm. I've been clean ever since.
Used to use Norton, lagged me like hell. Long start-ups, and decreased performance overall. I don't know why, though. o.o