"Show 3D Preview In 2nd Monitor" option doesn't work

In the preferences in WM2 Pro there is an option that says “Show 3D Preview In 2nd Monitor” but when I turn the check box on, nothing happens. This a feature that would be extremely useful to me, so I’m hoping that I can get it to work. Anyone have any ideas? I’m running the 64-bit version in Vista if that helps.

Any way how to make this feature work? I would find it extremely useful.