A video card (which supports OpenGL - a technique SU uses to display 3d) has a software called video driver (this will "run" it on you computer). This should be updated as I suspect that your Vista OS needs a different driver for the same video card from what XP needed. At those OpenGL settings you tell SU to exploit all the powers of your video card (use HW acceleration) or not (disable it). If you don't use all powers, SU may become slower. It's not always a big deal however (I have done considerable work on two computers whose video cards didn't have OpenGL support at all) but the one I'm using now has a nice card with an appropriate driver and I can indeed feel the difference.