If you run a Windows operating system such as Windows 98, Windows 2000, Windows XP, or Vista you should absolutely have an antivirus program installed on your computer, otherwise you are asking for trouble. I typically recommend Norton antivirus since it is the best out there. But there are also several other antivirus programs, which although not as good as Norton are typically much cheaper. 

If price is an issue, I have discovered a very good antivirus program that doesn’t cost anything. It is made by a company called Grisoft. If you want some more information about it or like to download it and give it a try here is their web site: http://free.grisoft.com 

Additionally, All Windows users should seriously consider purchasing Anti Spyware for their computer. It is still extremely easy for something to sneak on your computer without you knowing and do all sorts of nasty things. Spyware programs are also often very difficult to remove. The best program I have found for keeping your computer free of Spyware is SpySweeper from Webroot 

If you run Apple OS 8, 9, or 10.x you really don’t need an antivirus program. There are no known viruses for Apple OS X even though it has been available for over 5 years. However, it is good practice to have an antivirus program anyway so you don’t inadvertently pass along viruses (which don’t affect Apple operating systems) to people who use Windows operating systems. I have found a very good free antivirus program that I use to scan suspicious files and mail messages. It is called ClamX AV and a can be downloaded here by visiting the site.