Ubuntu 11.04 Natty uses Unity as default desktop environment, but this by no means the classic Gnome 2 desktop has been discarded. If you prefer this classic gnome desktop, you can do follow steps:

1.) At Ubuntu 11.04 login screen, choose login to “ubuntu classic”.

2.) Right click on “main menu”, “global menu” at top left screen and uncheck “lock to panel”, then select to “remove from panel”

3.) Right click on top panel, choose “add to panel” and then add “menu bar”.

Now you’re in Ubuntu 11.04 with classic gnome desktop!