The severity of damage done by the virus depends on the virus itself.  There are 10's of thousands of viruses in existence.  Some viruses simply make software work incorrectly while others may lay dormant on your system and then erase your entire hard drive on a particular date and time.  Luckily, protecting your computer is as simple as installing virus protection software and scheduling it to scan your system on a regular basis.  The two most popular programs are Norton Antivirus (www.norton.com) and McAfee Virus Scan (www.mcafee.com).  Both programs retail for about $50 and can be purchased online or at any office supply store.  I use Norton Antivirus 2000, which is now protecting my system from over 58,000 different known viruses!

Both programs not only come with a pre-determined set of virus "definition" files but also have the ability to automatically connect to the manufacturers website (on a regular basis) and update those definitions to include any new viruses which may have been recently discovered (over 20 new viruses have been identified in January alone).  I have Norton update its definition files once a week and scan my entire system once a week.  To learn more about the latest viruses discovered and how you can protect yourself, visit the Norton Virus Encyclopedia at http://securityresponse.symantec.com