If youv’e got a couple of programs open, dont you find it annoying when the programs form a group in your taskbar?
Like so-

If so, you can stop this happening by -
1. Right-Click on the Taskbar
2. Go to Properties, and Uncheck the Group Similar Taskbar Buttons box.

But if you are one of these people who like the programs to from a group, check the box.

Source : http://www.tutorialized.com/view/tutorial/Ungroup-Similar-Taskbar-Buttons/11543