I did not have much time to dig too deep into this, but here is some info to get you some direction:

These functions are related to general execution environment.
NtQueryDefaultLocale GetLocaleInfo Retrieves information about the locale.
NtSetDefaultLocale SetLocaleInfo Sets locale information. NtQuerySystemEnvironmentValue GetEnvironmentVariable Gets the value of an environment variable.
NtSetSystemEnvironmentValue SetEnvironmentVariable Sets the value of an environment variable.
NtQueryDefaultUILanguage New to NT 5.0. NT 5.0 supports on-the-fly language changes. Queries the current language.
NtSetDefaultUILanguage New to NT 5.0. NT 5.0 supports on-the-fly language changes. Sets the current language.