Want to see what Windows 7 may look like in your native language, and you have been frustrated by the lack of available language versions of Windows 7 RC? Be frustrated no more. Microsoft today released 31 Language Packs for Windows 7 RC through Windows Update;
As it is stated in the information on the Language Packs;
After you install this language pack, you can change the display language of Windows 7 to be (your chosen language), Go to the Clock, Language, and Region category in the Control Panel to change the display language.