The X. model probably got several groups, or the exporter of the x. model saves it in that way.
MED doesn't divide into different parts, at least not from my exports from blender as .fbx model.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt