How do I change Ubuntu's GUI?

Recently I installed a program to change Ubuntu's desktop but it went bad, so I uninstalled it but the GUI then had debris and stuff all around.

I had to reinstall Ubuntu completely. How do I change Ubuntu's desktop without messing up the system?


We have lots of different desktops. You can (click to) install xfce4, LXDE, Gnome Shell (includes Gnome Panel as "fallback") or any other desktop. You choose the desktop you want to use before logging in, by clicking on the button next to the password field.