AM window panes problem

I've somehow managed to rearrange my AM desktop so now the panes are stacked vertically instead of horizontally. I can't just move the contraptions back with my mouse, they are stuck in the lower half of my screen. This makes it frustrating as I can't see the layout in a nice horizontal flow. I've tried uninstall and reinstall, but it just reinstalled the desktop the same way. Can anyone tell me how to get the layout back to default please?