C3D is a file format used to store motion capture information. C3DServer is a useful program to view and analyze the information in a C3D file. It is free for non-commercial use.
The main program is called VB C3D Editor, named so possibly because it is written in Visual Basic. If you open a C3D file in it, it displays the header, event and the hierarchical marker information. Clicking on any marker shows the XYZ coordinates and plots over time.
Tried with: C3DServer 1.0.69 and Windows 7 x64