How to change gnome display setting
 

hello,
i was using GDE in my ubuntu system. But yesterday i did some thing so my ubuntu system has changed as debian. My login screen changed and i cant access "system->administration->Login window"
when i do this i am getting this error message
"GDM (GNOME Display Manager) is not running.
You might be using a different display manager, such as KDM (KDE Display Manager), CDE login (dtlogin), or xdm. If you wish to use this feature, then your system will need to be configured to use GDM instead."
Please help me. How to come back to my normal original ubuntu with GNOME.

Try - 'sudo dpkg-reconfigure gdm'

cheers