I am new to ubuntu and working with it is wonderful. I installed 12.04 kde in my laptop. To change kde to gnome i used "apt-get install gnome" command for gnome installation. After complete installation it asked me to select option between gdm and lightgdm. I selected lightgdm but after that i am not able to open neither kde nor gnome. But i am able to start virtual terminal tty1 using Alt+F1.
Now i don't know how to repair this. Please tell me how to repair my system to get back at-least kde which i installed. I am using UBUNTU 12.04 LTS.