That model comes with 8600M GT doesn't it? If so that should be plenty for a screensaver. With video cards, you sometimes get a default driver
installation from 7's install disc and that will only be enough to get you going with basic graphics. What you probably need to do is to find the newest drivers
and install them yourself. Failing this, you might be out of luck because video cards for notebooks are really not meant to be upgraded as you can obviously see why.