As far as i can see i am pretty sure it is the NeXuS dock included in winstep
A multi-level dock system, NeXuS sits front and center, providing super fast access to your most frequently used applications. Flexible options allow it to dock or float anywhere on the screen, providing a myriad number of "On Demand" possibilities. From it's generous use of situational context sensitive menus to it's advanced Drag-n-Drop support, NeXuS is not only easy to use - it's a joy! WinStep: Desktop Themes and Customizing Windows!