The latest versions of your OS have security fixes and higher default security settings. So it is very important that you are running the latest OS with all the latest updates installed. New versions of Mac OS are cheap and very easy to install. If you are on windows and using an OS less than Windows 7, then buy an upgrade knowing that the price it costs is nothing compared to the frustration of having your computer software damaged. Also, I am very uncomfortable with the next version of windows "metro". I believe that windows 7 will be the most popular version of windows for the next few years so it is a very good time to upgrade if you have not done so yet.