Советы по Delphi. Версия 1.4.3 от 1.1.2001

 printf("Cannot open process token, quitting [%lu].\n", GetLastError);
 return 1;
 }
 }

 // normally, I should get the size of the group list first, but ...
 l = sizeof rawGroupList;
 if (!GetTokenInformation(hTok, TokenGroups, &groupList, l, &l)) {
 printf( "Cannot get group list from token [%lu].\n", GetLastError);
 return 1;
 }

 // here, we cobble up a SID for the Administrators group, to compare to.
 if (!AllocateAndInitializeSid(&ntAuth, 2, SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS, 0, 0, 0, 0, 0, 0, &pAdminSid )) {
 printf("Cannot create SID for Administrators [%lu].\n", GetLastError);
 return 1;
 }

 // now, loop through groups in token and compare
 found = 0;
 for (i = 0; i < groupList.GroupCount; ++i) {
 if (EqualSid(pAdminSid, groupList.Groups[i].Sid)) {
 found = 1;
 break;
 }
 }

 FreeSid(pAdminSid);
 CloseHandle(hTok);
 return !!found;
}

int main {
 bool j, l;

 j = jerry_coffin_method;
 l = look_at_token_method;
 printf("NetUserGetInfo: The current user is %san Administrator.\n", j? "": "not ");
 printf("Process token: The current user is %sa member of the Administrators group.\n", l? "": "not ");
 return 0;
}

//****************************************************************************//

Как узнать язык Windows по умолчанию?

Одной строкой 

Nomadic лаконично отвечает:

GetSystemDefaultLCID

GetLocaleInfo

GetLocalUserList — возвращает список пользователей (Windows NT, Windows 2000)

Кондратюк Виталий предлагает следующий код:

unit Func;
interface

uses Sysutils, Classes, Stdctrls, Comctrls, Graphics, Windows;

////////////////////////////////////////////////////////////////////////////////
{$EXTERNALSYM NetUserEnum}
function NetUserEnum(servername: LPWSTR; level, filter: DWORD; bufptr: Pointer; prefmaxlen: DWORD; entriesread, totalentries, resume_handle: LPDWORD): DWORD; stdcall; external 'NetApi32.dll' Name 'NetUserEnum';

function NetApiBufferFree(Buffer: Pointer{LPVOID}): DWORD; stdcall; external 'NetApi32.dll' Name 'NetApiBufferFree';
////////////////////////////////////////////////////////////////////////////////

procedure GetLocalUserList(ulist: TStringList);

implementation

//------------------------------------------------------------------------------
// возвращает список пользователей локального хоста
//------------------------------------------------------------------------------
procedure GetLocalUserList(ulist: TStringList);
const
 NERR_SUCCESS = 0;
 FILTER_TEMP_DUPLICATE_ACCOUNT = $0001;
 FILTER_NORMAL_ACCOUNT = $0002;
 FILTER_PROXY_ACCOUNT = $0004;
 FILTER_INTERDOMAIN_TRUST_ACCOUNT = $0008;
 FILTER_WORKSTATION_TRUST_ACCOUNT = $0010;
 FILTER_SERVER_TRUST_ACCOUNT = $0020;

type
 TUSER_INFO_10 = record
usri10_name, usri10_comment, usri10_usr_comment, usri10_full_name: PWideChar;
 end;
 PUSER_INFO_10 = ^TUSER_INFO_10;

var
 dwERead, dwETotal, dwRes, res: DWORD;
 inf: PUSER_INFO_10;
 info: Pointer;
 p: PChar;
 i: Integer;
begin
 if ulist=nil then Exit;
 ulist.Clear;
 info := nil;
 dwRes := 0;
 res := NetUserEnum(nil, 10, FILTER_NORMAL_ACCOUNT, @info, 65536, @dwERead, @dwETotal, @dwRes);
 if (res<>NERR_SUCCESS) or (info=nil) then Exit;
 p := PChar(info);
 for i:=0 to dwERead-1 do begin
 inf := PUSER_INFO_10(p + i*SizeOf(TUSER_INFO_10));
 ulist.Add(WideCharToString(PWideChar((inf^).usri10_name)));
 end;
 NetApiBufferFree(info);
end;
end.