Umm for you people that say Norton is a resource hog and slows your computer down dramatically, here's something. If you're computer is actually decent with good CPU and RAM, resource hogs like Norton shouldn't really bother you. All the people that say Norton slows down their computer alot probably have bad computers. It doesn't cost alot to get a decent computer that can run well with Norton. Personally, I wouldn't go for Norton anyways, mainly because of it's low detection rate, and NOT because of the resources is uses.
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Anyways, I suggest looking into Bitdefender of Kaspersky for antivirus, Zonealarm is a good firewall, but I find it buggy. Also, one anti-spyware is never enough. The Anti-spyware programs I have on my computer are: Ad-Aware Se Pro, Xoftspy, Counterspy, and Spyware Doctor. All very effective.