https://stackoverflow.com/questions/58670/windows-cdrom-eject

C function

bool ejectDisk(TCHAR driveLetter)
{
  TCHAR tmp[10];
  _stprintf(tmp, _T("\\\\.\\%c:"), driveLetter);
  HANDLE handle = CreateFile(tmp, GENERIC_READ, FILE_SHARE_WRITE, 0, OPEN_EXISTING, 0, 0);
  DWORD bytes = 0;
  DeviceIoControl(handle, FSCTL_LOCK_VOLUME, 0, 0, 0, 0, &bytes, 0);
  DeviceIoControl(handle, FSCTL_DISMOUNT_VOLUME, 0, 0, 0, 0, &bytes, 0);
  DeviceIoControl(handle, IOCTL_STORAGE_EJECT_MEDIA, 0, 0, 0, 0, &bytes, 0);
  CloseHandle(handle);
  return true;
}