in Windows XP, entering g-dxf or any other conversion command in mged returns "invalid command name"
this occurs in both 7.14.8 and 7.12.6
thanks for your help.
The geometry converters are not accessible from within MGED. They are stand-alone external commands. Running them is a little more complicated on Windows, but still easy enough to accomplish. Open a command window and in your BRL-CAD installation directory, change to the bin directory and run the tool from there. E.g. Run cmd.exe then cd "C:/Program Files/BRL-CAD/bin" then g-dxf -o new.dxf yourfile.g some_object.