Change location of default folders editing user-dirs.dirs?

Change location of default folders editing user-dirs.dirs?

I have UBUNTU 12.04. I tried to change the location of default folders
(Documents, Music, ...) to other disk (NTFS-formatted). I tried to change
the file ./config/user-dirs.dirs. However, after reboot the changes in
user-dirs.dirs disappear.
For example, to change my desktop folder I wrote:
XDG_DESKTOP_DIR="/media/Datos/juanvi/Escritorio"
Note: Escritorio is Desktop in Spanish.
Maybe I cannot move the default folders to NTFS partitions?