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The system tray (or "systray") is a section of the taskbars in the Microsoft Windows desktop user interface that is used to display the clock and the icons of certain programs so that a user is continually reminded that they are there and can easily click one of them. The system tray is a section located at the one end of the taskbar in Windows 95, 98, and NT. Icons that are often installed in the system tray include the volume control for sound, anti-virus software, scanner software, a channel viewer, player, and a system resources indicator. When more icons are installed in the system tray than can fit in the space allotted, the system tray becomes horizontally scrollable or expandable. To interact with a program in the system tray, you select an icon with your mouse and double-click or right-click the icon. When you minimize the program after using it, it shrinks back into the system tray instead of into the main part of the taskbar.
What makes a system tray icon special is that, when installed, it can have a customized message appear when the mouse is hovering over it; the menu that appears when you right-click it can be customized; and the action that occurs when you double-click it can also be customized. For example, the double-click action for Internet Explorer could be to launch (start, or open a window for) the program, but the double-click action for a desktop icon could be to "View desktop," simply remove the active windows and show the underlying desktop.
An icon can be placed in the system tray when a program is installed by making an entry in the system registry or later by creating a shortcut to a program and dragging the shortcut icon to the system tray. An icon can be removed by deleting the registry entry or by right-clicking it and selecting Delete on the popup menu. The clock is removed by deselecting the show clock option in the taskbar Properties.