Hi Ivan,
Yes I get this message from the web UI. The exact message on the button is "Set RAID Type and Reformat" like when you insert a drive for the first time.
BUT ... I have found the solution !!!
When you reset your Unit; you have to insert another drive in the right side (the same as your initial disk) and format it as proposed by the web interface. When it's done, just shut down the DNS320, remove the newly formated disk and replace it with your original drive (with plenty good DATAs on it :-). Then boot the unit and you will see all your stuff back in the right place !
The rest of the actions are then easy, add users, groups, shares etc etc
Thanks for your answers anyway, this helped me to look in the good direction ^^
Bye