sudo apt-get purge xconf xfwm4 xfce4-session thunar xfdesktop4 exo-utils xfce4-panel xfce4-terminal libxfce4util-common libxfce4ui-common xfce4-power-manager-data xfce4-taskmanager sfpanel-switch xfdesktop4-data light-locker lightdm lightdm-gtk-greeter lightdm-gtk-greeter-settings xubuntu-default-settings liblightdm-gobject-1-0 plymouth-theme-xubuntu-logo plymouth-theme-xubuntu-text xubuntu-artwork xubuntu-community-wallpapers xubuntu-docs xubuntu-icon-theme xubuntu-wallpapers

sudo apt-get autoremove

sudo apt-get install xdm openbox obconf