Morphix reorders the vertices of one model to match the vertex order of another model. This obviously only works for models which share the exact same number of vertices, edges and faces. Also, the topology of both objects have to be the same.
The file contains rar files for both 3dsmax8 and 3dsmax9. Depending on the 3dsmax version you're using, extract either the max8 or max9 rar file in the root folder of 3dsmax and (re)start max. The script can then be assigned to a hotkey/toolbar/etc through the "Customize User Interface" dialog. The script is listed under the "MvH Tools" category.