A while back I noticed there was a German language patch available for Wing Commander 2 and decided to do the same for the French version of the game.
Just unzip this file to the Wing Commander 2 directory and play. Floppy disk versions must already be installed on the hard drive, although the zip will translate the installation menu text as well. Note that this only alters subtitles (both cinematics and in flight) and not speech. It's always a good idea to create a backup copy before overwriting too.