Language packs are available through Windows Update as optional updates. They aren't installed automatically.
Open Windows Update by clicking the Start button . In the search box, type Update, and then, in the list of results, click Windows Update.
In the left pane, click Check online for updates from Microsoft Update, and then wait while Windows looks for the latest updates for your computer.
If any updates are found, click Optional updates are available.
Under Windows 7 Language Packs, select only the language pack that you want (installing all of them might take up too much space on your drive).
Click OK, and then click Install updates. If you're prompted for an administrator password or confirmation, type the password or provide confirmation. You might have to restart your computer.