Did you know that the average new computer out of the box is hacked within 25 minutes of it being connected to the Internet.
Did you know that on a dial-up Internet connection your computer will be scanned by a hacker in less then 120 seconds on average.
Here is a step by step on what you need to do to protect your computer.
Do not use Internet Explorer or Outlook Express. They are the most highly targeted pieces of software on the planet. Insted use Firefox and Thunderbird.
Install a router between your cable/dsl modem and your computer(s).