You can configure vista display a message to users who are attempting to log on. For example, you may want to a message to appear that only Authorized Users Allowed
Click Start—>Administrative Tools—>Local Security Policy.
Within the console, expand Local Policies—>Click Security Options. The various security options are displayed in the right pane.Scroll through the options and locate Interactive Logon: Message text for users attempting to log on.
Double click the security option.Type in the message text that you want users to see.Click OK