1.First we need to do Update
# apt-get update
2.Then install the Desktop Environment , This Command will install the GNOME Desktop Environment
# sudo apt-get install ubuntu-desktop
3.IF we need to install the Desktop Environment Without installing some softwares like openoffice or Evolution Use this command to install minimum , Here im using this command Cos alreay i have installed liberoffice
# sudo aptitude install --without-recommends ubuntu-desktop
4.If You want to install light weight xubuntu Window
# sudo apt-get install xubuntu-desktop
5.If You want to install KDE Desktop Environment Use command
# sudo apt-get install kubuntu-desktop