The weakest Intel GPU that can support Aero was the Intel 945G. There is also the 915G that don't have a WDDM driver, which is even more of a problem now given

The weakest Intel GPU that can support Aero was the Intel 945G. There is also the 915G that don't have a WDDM driver, which is even more of a problem now given that they ditched XPDM support in Win8.