Also Need Help with trojan.zeroaccess, tojan.gen

Every few minutes norton is blocking trojan.zeroaccess.b, trojan.gen, and tojan.gen.2. I can't get on google and I couldn't even register on this website via my infected laptop because the captcha wasn't showing up. How do I remove the virus completely because norton's quarantine didn't seem to help. Why are so many people having this problem?