At the core of DirectX are its application programming interfaces, or APIs. The APIs act as a kind of bridge for the hardware and the software to "talk" to each other. The DirectX APIs give multimedia applications access to the advanced features of high-performance hardware such as three-dimensional (3-D) graphics acceleration chips and sound cards. They control low-level functions, including two-dimensional (2-D) graphics acceleration; support for input devices such as joysticks, keyboards, and mice; and control of sound mixing and sound output. Because of DirectX, what you experience with your computer is better 3-D graphics and immersive music and audio effects.
Download : DirectX Redistributable 9.0c November 2008 (Web Installer)
Download : DirectX Redistributable 9.0c SDK November 2008