Aspect Ratio Widescreen to normal

Hi, I have a widescreem set to 1680x1050 and when I play games I want my screen to be in normal 4:4. But when I change resolution it looks dizzy. It display a 1024x768 resolution into 1680x1050 and I know there is a way to set the (aspect ratio) to make it look normal. But no idea how to and I can’t see aspect ratio in my pannel. Thank You.