One of the features introduced in Windows 7 (or was it Vista?) is the capability of the taskbar button of an application to show the progress of a progress bar in that application. When I create a form and place a progress bar on it, it doesn't show up in the taskbar button, so I assume this isn't done automatically. How can I get Windows 7 to show the progress of a progress bar on the application's taskbar button?
It can be easily accomplished using the ITaskList3 COM Interface.
For using it in Delphi check the following link: Fun with the Windows 7 Taskbar
Also Check this link for complete article describing the features provided by ITaskList3 Windows 7: How to display progress bar on taskbar icon?
You can also use TTaskbarListProgress component from the TaskbarListComponents open sourced component pack. Released under the dwywbdbu license.
来源：https://stackoverflow.com/questions/8633389/how-to-get-applications-windows-taskbar-button-to-show-progress-of-progress-bar