If you have the WDDM drivers installed as Rick suggested and you still don't
get Aero, its possible you might have enable it manually. Right click your
Desktop > click Personalize > click Windows Color and Appearance > under
themes > select Windows AERO > OK.
If it still does not appear, try updating your Windows Experience Index
Score. Click Start > right click Computer > click Properties > click the
Update Score link, accept UAC message.