Verified answer

If you are doing this in Word 2007 you need to encrypt the file. To do this go into Word, click on the logo, select "Prepare" and then select "Encrypt File". It will ask you for a password (twice). If you lose the password it is not possible to open the document.

Note: if you have your own user account in Vista only you can open the file. However, the administrator can get around this by deactivating your password and then going into it. By encrypting it in Word it can only be opened using a password.

Hope this information helps.

What program is the diary in? Many applications have their own locking technology rather than relying on the OS