Blender Internal: How do I add motion blur? just wondering where to enable motion blur in the blender internal render engine.

It's supposed to be in the render settings called "sampled motion blur" but I can't find it.
I am using Blender 2.74

Download demo-file here.
Sampled motion blur is not available in Blender internal when the Full Sample option is enabled in Anti-Aliasing.

The solution is to turn off Full Sample.