Windows 7 Service Pack 1 language packs are available for computers that are running Windows 7 Ultimate Service Pack 1 (SP1) or Windows 7 Enterprise Service Pack 1 (SP1).

The Windows 7 language packs can be installed only from the Optional Updates section in Windows Update. However, these language packs are not available on the Microsoft Windows Server Update Services (WSUS) server or through the Microsoft Download Center.

When you install a language pack, you can change the interface language of Windows 7 SP1 to the language that you select.

More at KB2483139.