In order to install and use Shader Model 3.0 you need to have a graphic card that can support this technology. Therefore, you need to check if you own such graphical engine. In case that your GPU is not designed to support Shader Model 3.0, the only thing in this situation is to change it.
GpuZ can tell you exactly what the specs of your default graphic card are. The Shader Model (SM) version will be found in the DirectX Support information.