The GMA X4500 and the GMA X4500HD for desktop were launched in June 2008. The GMA X4500 is used in the G43 chipset and the GMA X4500HD is used in the G45 chipset. The GMA X4500 is also used in the G41 chipset, which was released in September 2008.
The GMA 4500MHD for laptops was launched on July 16, 2008. Featurewise, the 4500MHD is identical to its desktop cousin, the X4500HD. It had been previously rumored that a cost-reduced version, the GMA 4500, was to be launched in late 2008 or early 2009 and was to be used in the upcoming Q43 and Q45 chipsets. But in practice the Q43 and Q45 Chipsets also use the GMA X4500.
The difference between the GMA X4500 and the GMA X4500HD is that the GMA X4500HD is capable of "full 1080p high-definition video playback, including Blu-ray disc movies",
Like the X3500, X4500 supports DirectX 10 and Shader Model 4.0 features. Intel designed the GMA X4500 to be 200% faster than the GMA 3100 (G33 chipset) in 3DMark06 performance and 70% faster than the GMA X3500 (G35 chipset).
Source : http://en.wikipedia.org/wiki/Intel_GMA