A Windows slang term for a system tray icon which serves little to no purpose other than taking up precious screen real estate. Many name-brand computers will start up with as many as ten or more icons in the tray. Some are taken by devices and serve little purpose other than to say "This device is installed." For example, the IntelliPoint software for the Microsoft IntelliMouse installs a tray icon which launches the Mouse control panel. Many IBM ThinkPads come with tray icons for the NIC, IRDA port, and other such hardware devices. None of these software developers had heard of the Control Panel icon, apparently.
In Windows XP, tray trash is quickly whisked away to never-never land if "Hide Inactive Icons" is checked in the Taskbar Properties dialog.