You can put a password on the PST so no one can open it, but you can't use a
password to prevent someone from starting the Outlook application. Keep in
mind, though, that if you forget the password, you'll have to buy a tool to
recover that password and there's nothing to prevent anyone else from using
such a tool to get the password in your PST. In other words,
password-protecting the PST is only cursory security. The safer security is
to lock your account or log out when you leave the computer.
