Article in English: You can find this in the Start Menu. For older versions of Windows XP, select "Settings" to see the Control Panel option. If you are using Classic View, select "Regional and Language Options". This will allow you to change the options for your input language. If you are switching inputs to an East Asian language or a complex script language, check the appropriate boxes and click "Apply" to download the required extra files. This will open the Text Services and Languages Input menu. Select your desired input and language and keyboard layout from the drop-down menus. Click "OK" when you're satisfied. Your newly-added language will appear as an option in the "Default input language" drop-down menu. Select it if you want to change your input language now. Click "Apply" to save your changes. The Language Bar will appear automatically when you have more than one input language installed. You can find it in your taskbar, next to the system tray. Click the active language to see a list of all your installed input languages. You can also press Left-Alt+⇧ Shift to cycle between your installed languages.

Summary in Indonesian:
Buka Control Panel. Pilih "Date, Time, Language, and Regional Options". Klik tab "Languages". Klik tombol "Details". Klik tombol "Add". Pilih bahasa default Anda yang baru dari menu buka-bawah. Gunakan Language Bar untuk beralih antara bahasa masukan yang telah dipasang.