win 7 / win 8
right click desktop, click screen resolution:
now click on the monitor giving you trouble and under "resolution" find the one that says "reccommended" - which will most likely be 1920x1080.
Now for the placement, look at the little pics of monitors labelled 1 and 2 - this tells windows where your monitors are physically. Drag them to where they should be and click apply.
win 10?
Same thing, but to get there right click and hit "display settings" and then "advanced display settings"