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How do I reset my Unity configuration?

I'm just a newbie switching to ubuntu for a few day.
I accidentally turn off the unity interface in the ccsm (compiz something I don't know)
Now, my desktop don't have anything except my computer, home folder, and trash.
Many (or all) shortcut keys are disable.
I can only access the internet by going through folders in my computer.
And this place is my only last hope before I decide to reinstall it again.