rendering to displays that are not spanned by Windows desktop

[hosier]

How about this: On the first video card, display 1 is your windows desktop. The second port on the first card is your HMD. On the second card, span the two outputs into a single window, and use that for your passive setup.

I have something like that setup for a classroom. A Dell PC with two NVidia cards. The first card runs the main classroom projector and a side projector. The second card is setup for passive stereo viewing. We've arranged the windows so that the main display (1) is in the center. Display 2 is the spanned display from the second card, and it's on the left. Display 3, which is the second port of the first card, is on the right.

When the instructor wants to move something to the side projector, they just drag it to the right. If they want to show something on the passive stereo screen, they drag it to the left.

One thing you'll want to make sure you have set is the multidisplay performance mode. Otherwise the first display on a card gets pretty much all of the processing.

I guess now that I think about it, this probably doesn't really solve your not wanting to span the desktop. While they are seperate windows, in a way it is still a single desktop.

Aaron