Although the taskbar and application desktop toolbars normally constrain or clip windows displayed on the screen, you can define a window to the full extent of the display screen. Because this is not the typical form of interaction, only consider using full-screen display for very special circumstances, such as a slide presentation, and only when the user explicitly chooses a command for this purpose. Make certain you provide an easy way for the user to return to normal display viewing. For example, you can display an on-screen button when the user moves the pointer that restores the display when the user clicks it. In addition, keyboard interfaces, like ALT+TAB and ESC, should automatically restore the display.
Remember that desktop toolbars, including the taskbar, should support auto-hide options that allow the user to configure them to reduce their visual impact on the screen. Consider whether this auto-hide capability may be sufficient before designing your application to require a full-screen presentation. Advising the user to close or hide desktop toolbars may provide you with sufficient space without having to use the full display screen.