This is correct. This new functions is actually enabled within Vista drivers only in combo with NVIDIA ForceWare 163.67 and newer (163.71 works fine also). Rivatuner does never alter the registry or driver settings by default. And for XP NVIDIA disabled this functionality.

Now there is a quick an easy way to enable this cool function for Windows XP though. Do this:

In rivatuner (see above example) go to Power user | Rivatuner | System

Here set:

• NVAPIUsageBehaviour to 1
• NVAPIShaderClockControl to 1

Once you apply the settings and restart rivatuner you'll have the new slider available. Simply uncheck "Link clocks" to independantly set the clocks on the shader doamin. Enjoy.

Download Rivatuner here - http://downloads.guru3d.com/download.php?det=163