As a home computer user accessing the Internet, whether through a broadband connection or traditional dial-up, you should do the following three things at a minimum to protect your compute:

Install and maintain anti-virus software. There are plenty of great anti-virus software packages available. This software checks for known viruses by scanning your computer periodically. Most will also check for viruses on incoming email. It is important to update the software as well though.
New viruses are discovered almost daily. At least once a week you should check the web site of the vendor that makes your anti-virus software to see if there is an update available.

Do not open unknown or suspicious email. Many viruses and worms use what is called “social engineering”. That is, they attempt to trick you into becoming a participant in the process. The latest viruses can “spoof” the sending email address so that it looks like it is coming from someone other than the computer that infected it.
If an email is not from someone you know, it is usually best to simply delete it without looking at it. If the email appears to be from someone you know, you should read the message carefully before opening any attached files. Viruses and worms often have bad English and poor grammar. Consider whether the person you know would really have written that message or forwarded you the attached file. If in doubt, contact that person you know to confirm they truly sent it before opening the attachment.

Keep your computer patched against known vul