function IsFileInUse(const fName: TFileName): Boolean;
var
  HFileRes: HFILE;
begin
  Result := False;
  HFileRes := CreateFile(PChar(fName),
                         GENERIC_READ or GENERIC_WRITE,
                         0,
                         nil,
                         OPEN_EXISTING,
                         FILE_ATTRIBUTE_NORMAL,
                         0);
  Result := (HFileRes = INVALID_HANDLE_VALUE);
  if not Result then
    CloseHandle(HFileRes);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if OpenDialog1.Execute then
    if IsFileInUse(Opendialog1.FileName) then
      ShowMessage('File is in use!');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  if IsFileInUse('C:\Program Files\Adobe\Acrobat 7.0\Reader\AcroRd32.exe') then
    ShowMessage('Program lagi buka file yg tdk ingin saya ketahui, tunggu ya...xixixxixixixi');
  else
    ShowMessage('Program lagi nganggur...xixixxixixix');
end;

private
  procedure refresh;
{...}
function EnumWindowsProc(Wnd: HWND; lParam: lParam): BOOL; stdcall;
var
  aplikasi : array of Char;
begin
  if (IsWindowVisible(Wnd) or IsIconic(wnd)) and
    ((GetWindowLong(Wnd, GWL_HWNDPARENT) = 0) or
    (GetWindowLong(Wnd, GWL_HWNDPARENT) = GetDesktopWindow)) and
    (GetWindowLong(Wnd, GWL_EXSTYLE) and WS_EX_TOOLWINDOW = 0) then
  begin
    GetWindowText(Wnd, aplikasi, 256);
    if aplikasi <> 'GDI+ Window' then
      Form1.Listbox1.Items.Append(aplikasi);
  end;
end;
procedure TForm1.refresh;
begin
  Listbox1.Clear;
  EnumWindows(@EnumWindowsProc, 1);
end;
procedure TForm1.Button1Click(Sender: TObject);
var
  i,j : integer;
begin
  refresh;
  for i := 0 to listbox1.Items.Count -1 do
   begin
    j := Length(listbox1.Items.Strings[i]);
    if (copy(listbox1.Items.Strings[i],1,12) = 'Adobe Reader')
     and (listbox1.Items.Strings[i] <> 'Adobe Reader') then
     ShowMessage('Adobe Reader sedang membuka file : ' + copy(listbox1.Items.Strings[i],16,j))
   else
   if copy(listbox1.Items.Strings[i],1,12) = 'Adobe Reader' then
     ShowMessage('Adobe Reader sedang Nganggurr....xixixxixixi')
   end;
end;