→Why are my objects the wrong scale?
The best solutions is to figure out how to get your design software to export STL files in millimeters. In SolidWorks, for instance, the Save As dialog has an Options button, that allows you to set many parameters for exporting an STL.
If you cannot get your design software to do this, though, you can still rescale the part once you have it in MatterControl.
Edit the part, then choose Scale from the bar on the right. There is a drop down menu that will let you from many common conversion factors.
== Does MatterControl work on Windows XP? ==