This is independent of the software and is controlled by Windows. Poser or any other program can take advantage of a two monitor setup. Basically, Windows creates a screen size that stretches across two monitors and moving the cursor off the edge of one monitor brings it onto the next as if the monitors were connected. Tools could be moved to the second monitor and provide a full screen on the other for posing. Do use a Poser memory dot to save your single monitor configuration and another for your preferred two monitor state for Poser. That way, you can go back and forth easily between the setups depending whether you want to use one monitor or two.