Is there a way to make the Outlook Express in-box private, using a password?
You can password-protect your in-box using OEs Identities feature. From the menu select File | Identities | Add New Identity. Define a secondary identity, which you will not actually use; do nothing but give it a name. Do not switch to the new identity when prompted. Then select your own main identity and click on the Properties button. Check the Require a Password box and enter the password you want to use. Click on OK, then on Close.
After doing this one-time procedure, you must always close OE by choosing Exit and Log Off Identity from the File menu rather than merely selecting Exit. This menu item is disabled unless multiple identities are defined. (Thats why you created the nonfunctional secondary identity.) When you log off in this way, nobody can launch OE without supplying the password.
The initial release of Outlook Express 6.0 had a problem with switching identities. If you use version 6.0, be sure to update it with Service Pack 1.