In Pictures: Making the most of Windows 8 - the di...
Mitigating the misery of multiple monitors
Windows 8 doesn't handle multiple monitors well. The big obstacle is Metro, which runs on only one display at a time, by default the primary display. There's no way to span Metro across more than one screen. You can move Metro apps between displays by moving the Metro desktop itself. If you have Metro visible, press Win-PgUp or Win-PgDn to move it between displays. You can accomplish the same effect by clicking near the top of the Metro desktop when an app is open (the cursor turns into a hand) and dragging the app between screens. (Note: The margin at the bottom of the left-hand desktop is due to the difference in the size of the two displays).
In Pictures: Making the most of Windows 8 - the diehard's guide