Download the PC client for the DS708 and install it on a Windows machine that has an SD card slot. Put the blank SD card into the Windows machine, reformat it (Autel's suggestion), then start the PC software. Log in when prompted with the account you created to access this site. You should be able to create a new image on the card that will then be bootable. Once you can boot into the MaxiDAS, tap on "About" and you'll have the password needed to fulfill registration.
Chances are, however, that the device will be out of the support period and you might not be able to download any vehicle profiles. I'm curious how this turns out though--please keep up updated.
-Jeff