how to link a 2.4 blender file to the 2.7 blender version? I have tried linking older blender files to the newest version of blender and I get a warning saying that it is too old and it will not work with the recent version.
Have you tried to Save the old blender files into a new blender file? 

Try and open a new file in your newest version of blender. Then, just append every file from the Old blender file( of which you have problems linking) to the new blender file. Save that new file, and that should do it! It should work...