function GetWindowsLanguage: string;  
var 
    WinLanguage: array [0..50] of char;  
begin 
    VerLanguageName(GetSystemDefaultLangID, WinLanguage, 50);  
    Result := StrPas(WinLanguage);  
end;  
 
procedure TForm1.Button1Click(Sender: TObject);  
begin 
    ShowMessage(GetWindowsLanguage);  
end;  
 
{********************************************************************} 
{ another code: 
{********************************************************************} 
 
function GetWindowsLanguage(LCTYPE: LCTYPE {type of information}): string;  
var 
    Buffer : PChar;  
    Size : integer;  
begin 
    Size := GetLocaleInfo (LOCALE_USER_DEFAULT, LCType, nil, 0);  
    GetMem(Buffer, Size);  
    try 
    GetLocaleInfo (LOCALE_USER_DEFAULT, LCTYPE, Buffer, Size);  
    Result := string(Buffer);  
    finally 
    FreeMem(Buffer);  
    end;  
end;  
 
procedure TForm1.Button1Click(Sender: TObject);  
begin 
    Caption := GetWindowsLanguage(LOCALE_SABBREVLANGNAME);  
(* 
    LOCALE_ILANGUAGE           { language id } 
    LOCALE_SLANGUAGE           { localized name of language } 
    LOCALE_SENGLANGUAGE        { English name of language } 
    LOCALE_SABBREVLANGNAME     { abbreviated language name } 
    LOCALE_SNATIVELANGNAME     { native name of language } 
*) 
end;