Microsoft Office Assistance: Prevent embarrassment by hiding alerts during presentations: “Has this happened to you? You are in the middle of a demonstration or presentation and a New Mail Desktop Alert appears at the bottom corner of your screen, revealing information you would rather keep private.
Although Outlook 2003 will not display a Desktop Alert when you are running a PowerPoint 2003 slide show, if you switch to another program or a Web site during your presentation, Desktop Alerts and other notifications will resume displaying. Here is a quick way to prevent revealing personal information.”