Older versions of operating systems are not secure against modern Internet security threats.
Windows XP and MAC OS X have built-in tools for keeping track of critical security updates to their operating systems. You should configure these tools to download and install critical updates automatically. Doing so is easy and, once set up, requires little or no additional input from you.
*Make sure to choose a time when your computer is normally turned on.
Mac OS X automatically checks weekly for software updates, provided that you have an internet connection. You can chose a different schedule, or you can check manually if you do not have a continuous internet connection. If Software Update finds an item to download, it appears in a list. Click on an item to get a description before downloading it. If you see updates that you will never use, such as a language you don't speak or drivers for a printer you don't own, choose 'Make Inactive' from the Update menu. You can always view the hidden updates in case you discover you need them in the future.