const
{©Drkb v.3(2007): www.drkb.ru}
 FILE_DEVICE_FILE_SYSTEM: Integer = $00000009;
 METHOD_BUFFERED: Integer = $00000000;
 FILE_ANY_ACCESS: Integer = $00000000;
function CTL_CODE(DeviceType, FunctionNo, Method, Access: Integer): Integer;
begin
 Result := (DeviceType shl 16) or (Access shl 14) or (FunctionNo shl 2) or (Method);
end;
procedure TForm1.Button1Click(Sender: TObject);
var
 LHandle: THandle;
 BytesReturned: Cardinal;
 MsgBuf: PChar;
 FSCTL_LOCK_VOLUME: Integer;
begin
 FSCTL_LOCK_VOLUME := CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 6,
  METHOD_BUFFERED, FILE_ANY_ACCESS);
 LHandle := CreateFile('\\.\A:', GENERIC_READ or GENERIC_WRITE, FILE_SHARE_READ
  or FILE_SHARE_WRITE, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL or
  FILE_FLAG_DELETE_ON_CLOSE, 0);
 if LHandle <> 0 then
 begin
  if DeviceIOControl(LHandle, FSCTL_LOCK_VOLUME, nil, 0, nil, 0, BytesReturned, nil) then
  ShowMessage('Дисковод заблокирован. Нажмите ОК для разблокирования.')
  else
  begin
  if FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER or
  FORMAT_MESSAGE_FROM_SYSTEM, nil, GetLastError(), 0, @MsgBuf, 0, nil) > 0 then
  begin
  ShowMessage('Ошибка DeviceIOControl: ' + MsgBuf);
  LocalFree(Cardinal(MsgBuf));
  end
  else
  ShowMessage('Ошибка при вызове DeviceIOControl!');
  end;
  CloseHandle(LHandle);
 end
 else
  ShowMessage('Ошибка при вызове CreateFile!');
end;