This behavior is a known Windows issue in some systems after changing the display language. Since the display language, region, and copy settings were already configured, and a Reset did not fix it, the supported next steps are:
- In Settings > Time & language > Language & region, confirm Français (Belgique) is the Windows display language.
- Under Preferred languages, remove the other installed languages such as English and Dutch if they are still present.
- Restart Windows.
- If parts of Windows are still mixed after that, perform an in-place repair install of Windows 11 using a French Windows 11 ISO.
Important: back up files before the repair install.
For the in-place repair path described in the support guidance:
- Download the Windows 11 ISO in the correct language.
- Open the ISO in File Explorer and run Setup.exe.
- Choose the option to keep files and apps.
A normal Reset may not solve this because the recovery image can still contain remnants of the old language. An in-place repair install is the supported fix when Windows continues to show a mixed interface after the language has already been changed.
If the installed edition is Windows 11 Home Single Language, additional display languages are not supported. Check this in Settings > System > About > Edition. If it shows Windows 11 Home Single Language, Windows must be upgraded to Windows 11 Home or Windows 11 Pro to support multiple languages.
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