Ubuntu Natty 11.04 uses the Unity interface with 3D features. If your PC does not have a good graphics card or you want more speed out of your system you can install Unity-2D which has the same interface as 3D but without those resource hungry features like fancy shadows and many other things.

  • Open a Terminal ( crtl + alt + T )
  • Install Unity 2D with the following command
    • sudo apt-get install unity-2d
  • Confirm the download and wait until it’s finished
  • Now you should Logout and re-Login to see the results

If you are not happy and want to revert to either Unity 3D or even the classic Ubuntu menu just follow my other tutorial about Reverting from Unity to Ubuntu classic but if you want Unity 3D just choose Ubuntu from the sessions list.
{Tutorial} – How to revert the old Ubuntu menu in Ubuntu Natty 11.04

Another way to change your default interface is through Login Screen settings:

  • Go to 

    System -> Administration -> Login Screen
  • Click Unlock and type in your password
  • You can see at the bottom the dropdown list where you can choose the default interface you want

  • Choose the one you want and click Close
  • To apply the changes you must Logout and re-Login again

Enjoy :P