Yea a router is the best solution for firewalling (physical is better than software anyday). Until you get one I suggest using the built in Windows security center firewall that comes with SP2, plus all of the critical security updates. It is totally sufficient. The best free spyware removal is Spybot Search and Destroy, which can detect spyware, trojans, dialers, and much more. Also, it can immunize you against threats. The second best free tool is AdAware SE, which is updated less frequently as Spybot S&D.
The best pay adware removal tool is Ewido Security Suite.
I haven't used Anti Virus for 5 years, and I have never had a virus. Just be careful on the 'net, and don't look at a bunch of different porn sites. If you must go for anti-virus, my favorite, while factoring in resource usage and cost (free) is Anti-Vir. This is a German app, but there are English versions. Back in the day you had to use the German version, that really sucked......
Anything Symantec is crap, uses many resource hogging services
BTW you wanna know something messed up? When I had two roommates, we used his desktop before I got my new one (I'm still trying to fix my laptop). So I go half on a router (Linksys) for $50 at Walmart.....this guy waits until I visit my parents and takes the router back for in store credit, and IT WASN'T EVEN HIS PC! Needless to say, I don't live with those losers anymore.
I agree halfway with the above poster (no anti-virus), but no firewall just doesn't make sense. You will be overloaded with popups and spyware......
Oh yea I forgot LOL Bitdefender is pretty good, but it was too much for me. I don't want any processes running at all, which is why I would say just get a router.
Also, if you use Bittorrent protocol, get Peerguardian 2 FOR SURE!!! Unless you want your ISP to ride your you know what....
http://phoenixlabs.org/pg2/
Get the regular version, I've never run the lite. They have updates several times a day.