How to install another language?

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http://askubuntu.com – I'm trying to change the language for a standard user account. With the administrator account, I installed a new language by going to system settings > language support > install / remove languages. Then I logged in to the standard account, and moved the new language to the top by dragging it with the mouse. And then I reseted the machine and logged back in. But nothing changed. The new language is at the top of the list, but all the menus are still in the original language. Any ideas? (HowTos)