{$IFNDEF WIN32}

 const WF_WINNT = $4000;

{$ENDIF}

function IsNT : bool;

{$IFDEF WIN32}

var

  osv : TOSVERSIONINFO;

{$ENDIF}

begin

 result := true;

{$IFDEF WIN32}

 GetVersionEx(osv);

 if osv.dwPlatformId = VER_PLATFORM_WIN32_NT then exit;

{$ELSE}

  if ((GetWinFlags and WF_WINNT) = WF_WINNT ) then exit;

{$ENDIF}

 result := false;

end;

procedure TForm1.Button1Click(Sender: TObject);

begin

 if IsNt then

  ShowMessage('Running on NT')

 else

  ShowMessage('Not Running on NT');

end;

function IsNT: bool;
var osv: TOSVERSIONINFO;
begin result := true;
 GetVersionEx(osv);
 if osv.dwPlatformId = VER_PLATFORM_WIN32_NT then exit;
 result := false;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
 if IsNt then
  ShowMessage('Running on NT')
 else
  ShowMessage('Not Running on NT');