Before you install Windows

If you are installing/reinstalling windows it is important to remember that until you download all of the security updates your computer is very vulnerable (and yes it can take only minutes before something will try to attack your machine). So the way to get around this problem is to physically remove the ethernet cable from your computer before installing windows. Then once it is installed follow these instructions:
Step 1: Use an Internet Firewall

Once the firewall is on you can begin the exciting task of getting all of the security updates (at this point go ahead and plug the ethernet cable back in). Once you have all of the updates you might want to try leaving the firewall on, but you will probably find that lots of internet applications will not work, if that's the case go ahead and turn the firewall off.

If all of this sounds like a pain it might be time to look at this:
Mac mini