Vista already had this feature -multiple instances of applications were grouped into a single icon to save taskbar space. In Windows 7, the icons lie more distinguishable. You no longer have to click; you can simply move your mouse over the icon and a real-time preview of each of the instances will appear. The window can be closed by middle-clicking on the preview. If you like to have the application name appear along with the icon, right-click on the taskbar and click on Properties. Choose the Never combine option from the menu.