To use d3d9 you must link to d3d9.lib.
Link to d3dx9.lib is a helper library which you may also wish to use.
The d3d9 and d3dx9 header files must be included to make use of the functions contained within these libraries.

#include <d3d9.h>
#include <d3dx9.h>

Initializing Direct3D:

First declare a pointer to an IDirect3D9 interface object.

IDirect3D9* d3d9;

This interface is used to acquire information about the graphics hardware in a system and to create an IDirect3DDevice9 interface.

To create this interface call Direct3DCreate9 and pass it D3D_SDK_VERSION, this is the only real parameter and assures the application is built against the correct header files.

d3d9 = Direct3DCreate9( D3D_SDK_VERSION );