Microsoft issued two patches allowing Windows vista 32 and 64-bit user to update their DirectX towards DX11 with Compute Shaders activated.
Overview - The Windows Graphics, Imaging, and XPS Library contain the latest advancements in modern graphics technologies for gaming, multimedia, imaging and printing applications. It includes updates to DirectX, DirectCompute, and XPS Library. After you install this item, you may have to restart your computer.
Please make sure you have Windows Vista Service Pack installed. The download contains both the 32-bit and 64-bit patches.