user-dirs.dirs doesn't work like that.
~/Documents is just a directory on the file system. The thing it changes are the icons in Nautilus, bookmarks etc. So, when you go to Nautilus and click the Documents directory (I don't know what it will be called, it's a long time ago that I used translated directory names) you should get to where you want.
It seems to me you actually want something different. For example, when taking
~/Documents, what you could do is use this in
And let point
ln -s /media/E/Administrateur/Mes_documents/ ~/Documents
These are commands you can enter in a terminal (just search for 'terminal' in the dash).
What this does, is that creates a symbolic link named
~/Documents that points towards
/media/E/Administrateur/Mes_documents/. In effect, applications (like Nautilus) think they're looking at
~/Documents but they're actually looking at a different directory, somewhere else on the file system (or on a different filesystem, which seems to be the case here). You can use this also for the rest of the directories.
I think the Desktop directory is a bit of an exception. As I understand it, the desktop is just Nautilus running full-screen without toolbars etc. behind all other windows, showing the directory specified in
user-dirs.dirs. That's the reason (I think) why the desktop works. (Note, ~/Desktop would probably still be empty).
I recommend you also put a real Pictures and Videos dir. Otherwise, some applications might get confused.
More about symbolic links: http://www.linuxchix.org/content/courses/filesystem/Lesson2a.html