Okay. Push ctrl+alt+f1 to get to a terminal. Login with your username and password. Check your log files in /var/log
cat /var/log/Xorg.0.log | grep EE
This will only display error lines in the xorg log file - post these up.
To return your original configuration:
sudo cp /etc/X11/xorg.conf.backup /etc/X11/xorg.conf
Replace xorg.conf.backup with the file name of your backup.
This should return your original configuration, and give you a desktop which you can work from. Reboot the computer with:
Hopefully you will have a nice shiny desktop.