By default windows does not allow to opened applications and windows listed in taskbar to rearrange and shuffle to change the position. But there is a free application named taskbar shuffle which lets you reorder the taskbar items.
Taskix is another free application which solves the same purpose of moving taskbar opened items, allows you to reorder the taskbar tabs and change their positions in taskbar.
More over this small program provides more functionality other than just moving the taskbar opened applications and windows.
Some Key Features Of Taskix
1. You can scroll through taskbar tabs with mouse wheel
2. Close Taskbar item tabs with middle mouse click
3. You can show desktop upon clicking it