When you hover over or click a program in the task bar, if there are multiple windows, it will bring up the popup showing all of the open windows for that program. However, I would also like to be able to bring up all windows for that program by double clicking the icon in the task bar. I think that would be a nice feature.
But it already kinda does that... If you hold the mouse over say, IE 8's icon on the taskbar and if you've got multiple tabs open, you'll see a thumbnail of each one. If you double click on the icon itself, it will toggle hiding and showing those thumbnails.
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