(2-part post):
The site search hasn't been working for over a week so it's not surprising that it's not showing any similar questions ;-)
Yes, this has been asked hundreds of times before. While there might be a few dissenting voices, the majority of ABers seem to agree that you don't need to pay anything for decent security software. (In particular, some of the paid-for products from Norton and McAfee are regarded as worse than many of the free products, because they tend to slow computers down).
There's also a general consensus that the Windows firewall is 'a bit of a joke'. The most popular firewall, with ABers, is Zone Alarm Free Edition:
http://www.zonealarm.com/store/content/company /products/znalm/freeDownload.jsp
(NB: Use the link in the right-hand column. The other, more prominent, link takes you to a time-limited trial of a commercial product).
The principal alternative to Zone Alarm, which is used by some ABers, is Comodo:
http://www.personalfirewall.comodo.com/downloa d_firewall.html