I am running Linux-mint 13 with XFCE. When I drag a window to the side of the screen it snaps to the side and fills up that vertical half of the screen.

This is great, but I have two graphics cards so I can have two monitors. I can't drag a window from one monitor to the other because it snaps to the side of the the first screen. I have to open applications on the 2nd screen, and then they are stuck there.

I assume I need to disable this feature (even though I quite like it). I can't find any option for it anywhere. How do I do this?

Thank you.