Windows 8.1 - Prevent windows from being re-arranged when moved to the edge of the screen (Disable Aero Snap)
When you move an application window at the edge of your screen, it will automatically be resized (e.g full screen when moved at the top of the screen)
To disable this feature under Windows 8.1 follow the below procedure:
Open the Control Panel > Ease of Access Center.
Click on Make it easier to focus on tasks.
Scroll to Make it easier to manage windows.
Untick the Prevent windows from being automatically arranged when moved to the edge of the screen checkbox.