In addition to applying necessary security patches to Internet Explorer, Outlook and Outlook Express on a regular basis, you should "harden" your email software by disabling the capability of scripts and other programs to run automatically.
Netscape users also need to do this.
Ensure the propoer security settings by following the instructions for whichever software you use for email:
Outlook and Outlook Express
Tools | Internet Options | Security | Restricted Sites | Custom Level
NOTE: Just setting the restrictions to High will not work. If you are unable to follow this step, it may be a good idea to ask an experienced friend for assistance.
Basically, you need to set everything that says ActiveX, Java, Download, Install and Launch to "Disable".
After making the necessary changes to the Restricted Zone, you will need to add Outlook or Outlook Express to the Restricted Zone by doing the following:
Open Outlook Express or Outlook (if not already open)
On the menu, click Tools | Options | Security
Then, simply select the "Restricted Zone".