This is really a software question, not a notebook question, but I'll try to help a bit.
Doing this is going to depend entirely on whether or not the program you're using to play the video supports what you want to do. Many apps try to preserve the original aspect ratio, even if it doesn't fill the screen. You'll have to go into a preferences or options of the program and see if you can force it to stretch the video.
Personally, I don't feel the urge to distort the image just to feel like I'm getting a little bit more out of my laptop screen!