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Repeat the process for the "InstallLanguage" key. This can usually be found at the bottom of the list of keys. Use the same code that you used for the "(Default)" key.
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Close the Registry Editor and restart your computer. You must restart before you proceed, or the Service Pack 3 installation will not work.
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Run the Service Pack 3 installer after restarting. Once you have rebooted your computer, run the Service Pack 3 installation. It doesn't matter if you already have Service Pack 3 installed, as the installer will just overwrite the system files with the new ones in the correct language. Follow the prompts to install the Service Pack.
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Reboot your computer again after installing Service Pack 3. After the installation is complete, you'll need to reboot your computer for the changes to take effect. Once the computer has rebooted, you should be able to see the changes to your display language.
You may notice that some elements are still in the original language. This is a limitation of the workaround. The only way to completely display a different language is to reinstall Windows XP and select the correct language during installation.
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Download a Language Pack after changing your base language (optional). If you performed the above steps to change your base language in order to install a Language Pack, you can download and install it now. See Step 1 of this section for details.
Part 2 of 2:
Input Language
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Open the Control Panel. You can find this in the Start Menu. For older versions of Windows XP, select "Settings" to see the Control Panel option.
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Select "Date, Time, Language, and Regional Options". If you are using Classic View, select "Regional and Language Options".
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Click the "Languages" tab. 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.
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Click the "Details" button. This will open the Text Services and Languages Input menu.
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Click the "Add" button. Select your desired input and language and keyboard layout from the drop-down menus. Click "OK" when you're satisfied.
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Select your new default language from the drop-down menu. 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.
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Use the Language Bar to switch between installed input languages. 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.[2]
You can also press Left-Alt+⇧ Shift to cycle between your installed languages.