Human beings are more like computers than you think. They both are constantly losing things and they both fall asleep at the most unlikely times! Lastly, they both are susceptible to viruses.
So, "what are viruses and how do computers catch them?" you may ask. Well, viruses caught by computers are much like those that can be caught by humans. One difference is that, while humans get viruses from each other, computer viruses, such as "Luv Bug" (which has "I love you" in the subject line and wipes your hardrive if it is opened) are spread over the internet . "Mydoom" is another virus which periodically opens up your web browser and goes to specific sites(in order to overload them).
As a rule one should, NEVER OPEN UP ANY ATTACHMENTS WHICH HAVE BEEN SENT BY PEOPLE YOU DO NOT KNOW. Because, once you have you shall suffer the consequences. Once a virus has latched on to your computer, there is very little you can do! Though, one thing you can do, that will help, is contact Norton Anti-Virus (if you have it). Norton Anti Virus deals with both, major viruses and ones that are not as big. Yet, although Norton does the job well it is very costly and you should think twice about purchasing it. For, there are many other programs that are less costly, and in some cases, even free (such as AVG) which will also do a good job!
For more information on computer viruses you can visit:
http://securityresponse.symantec.com/