How come it doesn detect my nVidia/ATI/whatever graphics card?
Because the guest sees a virtual graphics card, not the host graphics card. The virtual graphics card provides the necessary VESA and VGA features to make the guest operative systems work OK. Additional features, like higher resolutions, is provided by the graphics driver included with the guest additions. More details on how to install guest additions and features of the virtual graphics card can be found in the manual.
