Since the release of AutoCAD 2004, you no longer had the capability to SAVE AS Release 14 AutoCAD format. This was a decision made by Autodesk to persuade legacy users to upgrade their R14 version of the program. Those user who did upgrade were complaining that they could no longer convert drawings for those users that never made the switch.
Therefore, Autodesk has released DWG TrueConvert. This is a free application that can be downloaded directly from the Autodesk Website. It is used to convert AutoCAD drawing files (.DWG) to legacy formats like 2000 or R14. It is a very useful tool if you were to ever receive drawings created in AutoCAD 2004 or 2005 that had not been converted to 2000 format.
The Batch Drawing Converter is a separate program. AutoCAD does not need to be open to use this application. After installation, go to the START menu --> Programs-->Autodesk-->Migration Tools-->Batch Drawing Converter.
Once in the application, ADD all the DWG files you need to convert, choose the appropriate conversion (R14 or 2000) and click on the CONVERT button. That's it!
To download the application click here: DWG TrueConvert