Windows XP Pro came with Encrypting File System (EFS) feature that lets you to encrypt your files so that no one else can read them. With EFS you can encrypt only the files and folders of your choice; you can encrypt a single file or folder, or all of your files and folders. Encrypted files and folders show up in Windows Explorer as green, so you can tell at a glance which have been encrypted.
You can work with encrypted files and folders transparently. In other words, after you encrypt them, you open them and close them as you normally would any other file. They’re decrypted on the fly as you open them, and then decrypted as you close hem. You’re the only person who can read or use the files. Encryption is tied to your account name, so even other accounts on the same computer won’t be able to read or use them, unless you specifically grant access to certain accounts.