hi
first let know what windows u use, if windows 7 then go on desktop and right click chose Personalize - Display, u can see it below in the left side then change display setting, now look in the right side and hit Advanced settings, after that its will show up what GPU u had ,,or try this remove nvidia drive from ur laptop and go nvidia website, search for ur GeForce GT555m and download it then install it, GoodLuck