Despite their name, personal computers aren't always that personal. You may have to share your machine with others. This can be a problem if you need to keep some of your data private.
Encryption can help: it scrambles data and stores it in a format that other people can't easily access. Microsoft Windows XP Professional Edition comes with encryption but the Home Edition doesn't. You encrypt files or folders by right-clicking on them and selecting the "encrypt contents to secure data" check box under the Advanced tab.
XP encryption isn't perfect. First, it only works if you use the NTFS file system. Second, files are not password protected, they are available to you as long as you remain logged on to the system. Other people can view them if they use your log-in and strangers may see the files if they wander up to your computer while you are logged on but not actually working on the machine.
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How to keep data private 
