type
  PTOKEN_GROUPS = TOKEN_GROUPS^;

function RunningAsAdministrator (): Boolean;
var
  SystemSidAuthority: SID_IDENTIFIER_AUTHORITY = SECURITY_NT_AUTHORITY;
  psidAdmin: PSID;
  ptg: PTOKEN_GROUPS = nil;
  htkThread: Integer; { HANDLE }
  cbTokenGroups: Longint; { DWORD }
  iGroup: Longint; { DWORD }
  bAdmin: Boolean;
begin
  Result := false;
  if not OpenThreadToken(GetCurrentThread(), // get security token
  TOKEN_QUERY, FALSE, htkThread) then
    if GetLastError() = ERROR_NO_TOKEN then
    begin
      if not OpenProcessToken(GetCurrentProcess(),
      TOKEN_QUERY, htkThread) then
        Exit;
    end
    else
      Exit;

  if GetTokenInformation(htkThread, // get #of groups
  TokenGroups, nil, 0, cbTokenGroups) then
    Exit;

  if GetLastError() <> ERROR_INSUFFICIENT_BUFFER then
    Exit;

  ptg := PTOKEN_GROUPS( getmem( cbTokenGroups ) );
  if not Assigned(ptg) then
    Exit;

  if not GetTokenInformation(htkThread, // get groups
  TokenGroups, ptg, cbTokenGroups, cbTokenGroups) then
    Exit;

  if not AllocateAndInitializeSid(SystemSidAuthority,
  2, SECURITY_BUILTIN_DOMAIN_RID, DOMAIN_ALIAS_RID_ADMINS,
  0, 0, 0, 0, 0, 0, psidAdmin) then
    Exit;

  iGroup := 0;
  while iGroup < ptg^.GroupCount do // check administrator group
  begin
    if EqualSid(ptg^.Groups[iGroup].Sid, psidAdmin) then
    begin
      Result := TRUE;
      break;
    end;
    Inc( iGroup );
  end;
  FreeSid(psidAdmin);
end;