Hi,
Three other parameters would be nice to know: a)your operating system b)your current version of Vizard c) the version of your nVidia graphics card driver
If Vizard is not stretching the output over the two monitors, this usually means that the 'horizontal span' mode is not activated in your nVidia driver. Please have a look at our nVidia driver support page at
http://www.worldviz.com/support/hardware_faqs.html
If you don't use the nVidia horizontal span mode, you will also notice that the frame rates for your simulation will drop significantly, as the 'Windows way' of handling dual monitor support does NOT provide proper openGL acceleration for both screens.
Hope that helps,
Matthias