I know this is not a beta 10 problem but it is the beta that introduced the 'display on monitor x" dialog... (I think).
....
My secondary screen is the "old" one I used to have....
I think you will find that Jim will tell us that that is a 'Windows' feature! - If I remember correctly, that's what he told me when I first reported how MA3 worked across two screens.
As regards the "old" secondary screen. -
You now have an excuse to justify a second 22" wide screen!!! 