Just a note or more on mrrockford's setup.
1. I usually do not recommend using Spybot S&D's TeaTimer because it can interfere with other security software. You can refuse to install it during Spybot's install or turn it off afterward from the Advanced menu in Spybot. It is fine to use all the other features in Spybot.
2. As an alternative to ZA, these days I am recommending OnlineArmor Free from TallEmu. IMHO, it is a better firewall and uses less resources than ZA.
3. If possible I recommend using the paid version of MBAM which adds two important features - real time protection, and automatic scans and updates. It is the least expensive of the paid antimalware packages, and one of the easiest to use and most effective ones as well.
4. An alternative to AntiVir (which I also use) is Avast! AntiVir and Avast! tend to score about the same on all the a/v testing, usually in the top performers, so if you don't like one, try the other. Remember, never use more than one a/v (or software firewall) because they will interfere with each other and neither of them will likely be providing protection.