Caution on Firmware Upgrade for ND2730
The firmware upgrade of ND2730 is composed of two step.

When user select firmware upgrade at the menu, ND2730 create small temporary data to the internal HDD then turn off the power.
Note that firmware is not written to the internal ROM until now.

At next power up, the stored temporary data is retrieved from the HDD then written to the ROM.

So if you remove the HDD just after firmware upgrade, then that will result in firmware upgrade fail.

Be sure to power up again without removing the internal HDD after the firmware upgrade.