Waltorious: It should go fullscreen automatically, so if it doesn't, you probably need to change some settings with your video card.
Go to your video card settings, and look for something called "flat panel scaling" or similar. In your case it's probably set to "off". What I recommend is setting it to "preserve aspect ratio", that way it will stretch the image to fill your screen vertically but will keep black bars on the sides so the image doesn't get stretched horizontally.
Post back and let me know if that works.
I'm really a console player uh hum PS3... This is all new to me as I'm a Fallout 3 and Vegas fan and thought I'd give the oldies a shot... And it worked thanks! :)