Force selected system UI language to overwrite the user UI language
This policy setting controls which UI language is used for computers with more than one UI language installed.
If you enable this policy setting, the UI language of Windows menus and dialogs for systems with more than one language is restricted to a specified language.
If the specified language is not installed on the target computer or you disable this policy setting, the language selection defaults to the language selected by the
If you disable or do not configure this policy setting, there is no restriction of a specific language used for the Windows menus and dialogs.
At least Windows Vista
In Registry Editor we can see the following changes:
For Enabled we get:
FullKeyPath : HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\MUI\Settings
ValueName : MachineUILock
Value : 1
For Disabled we get:
Value : 0