Hi! kasuya, welcome to W7F
First I need to ask:
Your sure the language pack installed correctly? Because you need to have Windows 7 Ultimate or Windows 7 Enterprise to change the display language.
Not sure if Gamer Edition is allowed.
Have you tried:
Control Panel\All Control Panel Items\Fonts
You can see font settings to your left of the window. click that, and then un-check the "hide font based on language settings" box.