Playing fullscreen games on widescreen laptop without stretching?

I have a laptop with a widescreen (16:10 ratio). I want to change to a 4:3 resolution (such as 1024x768 px), to prevent stretching. I have tried different drivers with no success. How do I accomplish this feat?

I remember having pulled off this stunt once by using a resolution-changing application, which added black masks to the left and right sides of my widescreen, thus creating a more conventional screen aspect ratio. However, I do not recall the name of this application. Any help would be greatly appreciated.