This tweak disable the Taskbar Grouping behavior.

To do this, follow the next steps:

1. Open the Registry Editor click on the Start button on your taskbar, then click on Run and type "regedit" and click on OK to start the regedit utility.
    
2. Expand HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced (see picture 1).
   
   

   Picture 1

3. In the right part of the window double click the keys "TaskbarSizeMove" and "TaskbarGlomming" and change both values to "0".
    
4. The modifications you made will be in effect after you reboot your PC.