But not _impossible_, as the poster implied.
As it happens, I don't recall the last time I played a DVD on my computer - I have a dedicated player for that - connected to a 50" screen.
Is DX10/11 needed for Visual studio?
According to that article heterogeneous multi-adapter will work in Vista/W7 if you use XPDM drivers instead of WDDM drivers.
At least that's my understanding of this:
A user could force the installation of a XPDM driver for each of these devices, and therefore get heterogeneous multi-adapter multi-monitor to work as in Windows XP.
I currently have a Quadro FX 570 and a GeForce GTS 250 installed. Once the different drivers were installed I had no problems with them both operating - both on Vista and now that I have upgraded to Win 7. I don't know what gave you the strange idea that it wouldn't work.
Two is not equal to three, even for large values of two.