MoldWorks runs within SolidWorks. SolidWorks is the 3D design package, while MoldWorks is the optimization package for insjection design.
It allows you to specify injection pressure and temperature, size your sprue-tree, find the proper location of ejector ports, comes with a huge material library, ect. It is a very comprehensive package, and coupled with SolidWorks, makes for a very powerful tool. "Happy the Hare at morning for she is ignorant to the Hunter's waking thoughts."