[RegionalSettings]
Language = locale ID
LanguageGroup = language group ID, language group ID
SystemLocale = locale ID
UserLocale = locale ID
InputLocale = locale ID:keyboard layout ID, locale ID:keyboard layout ID
UserLocale_DefaultUser = locale ID
InputLocale_DefaultUser = locale ID:keyboard layout ID
How to create the regional and language settings for an unattended installation of Windows MultiLanguage Version
[LEFT][RegionalSettings]
LanguageGroup="1","13"
SystemLocale="0409"
UserLocale="0409"
InputLocale="0420:a0050420","0420:00000401"[/LEFT]