The default desktop environment for Ubuntu 11.04 (Natty Narwhal) Unity. While Unity itself is great, some might prefer the old GNOME 2.8.x desktop environment.
In Natty Narwhal, GNOME 2 is installed by default. To login to GNOME 2 session instead of Unity, follow these steps;
After selecting the user, the option to choose the desktop environment will be made available at the bottom of the login screen.
Ubuntu Classic Desktop.