Is the d2's OS installed on the HDD, or on a flash chip on the mobo? If on flash chip, you can just replace the HDD (after formatting it); if on HDD, then you will have to copy the system partition (the one that has the OS on it) to the new HDD before inserting it. Without that, the system will not boot.
... LacieD2net OS is installed on internal HDD.
I've mount both HDD (original-LacieHDD and new-HDD) in computer and
... create same partitions on newHDD with Gparted. (/dev/sda1....../dev/sda10)
...than copy OS files with "Ubuntu" to new HDD.
...and install newHDD into LacieD2net.
But D2net do not startup with newHDD.
Should I mark some of linux patition on newHDD as bootable?