How to switch back to classic mode? [duplicate]

Possible Duplicate:
How do I switch to the Classic GNOME Desktop?
How to revert to GNOME Classic?

I don't like both of Unity and Gnome 3, but I can't find the classic one either, after installed Gnome 3.

The only choices are:

Fluxbox
Gnome shell
Recovery mode
User defined session

So how to get back the classic session?