Taskbar buttons represent open programs on your computer. When you have several programs open at once, the taskbar might seem crowded with buttons. To help organize the taskbar and save space, you can group similar taskbar buttons so that all of the open files from one program are grouped into one taskbar button, like this:
Open Taskbar and Start Menu Properties by clicking the Start button , clicking Control Panel, clicking Appearance and Personalization, and then clicking Taskbar and Start Menu.
Select the Group similar taskbar buttons check box so that it is checked. (To turn off grouping, clear the Group similar taskbar buttons check box.)