How do I update my Dell Video/Graphics card?

I have a Dell Inspiron 1545 and I have recently bought a game, but when I try to run it, it says: 'Error: Could not init 3D system. Shader Model 2.0 is required. Please install the latest video drivers.' I've tried to look for updates, but I'm not sure which video card I have. I've tried to use the Dell website to work out what I have, and update to get, but I can't get it to work. Does anyone know?