Screen resolution changes on playing Need For Speed

Recently I downloaded Need For Speed Most Wanted 2005 on my Laptop running Windows 8.1.When I play the game, the screen goes blank after a while and on returning to desktop, the screen resolution automatically changes to 720 X 1024 and orientation changes to portrait. What could be the reason?
i tried “Nfsmw res” the resolution problem solved but orientation problem is still there.