Set the following option to make the default file save type 2000-2002 Drawing:

Tools->Options->System Options->Open/Save As->Default file types->Save documents as type: set to R2000-2002 Drawing.

Click File->Save.  Resulting file is still a version 2010 drawing.

Click File->Save As - the file type will be set to 2000-2002 Dwg.  Click on Save - Resulting file will be a version 200-2002 Dwg.