I would go to Settings/ About and  retrieve unit's serial number and register password then call Autel Support in the USA and see if the unit can still be registered and  the final versions of DS708 software down loaded any longer.

Before doing so You might want to buy a brand new 16gb  Sandisk SD card and save the original card (albeit Ford doesn't work) as a backup before trying anything.You  never remove an SD card unless unit is powered off. Copy and paste the contents of the original 4gb  or 8 gb SD card to the new 16gb Sandisk SD card, and make sure the new card with copied software works

  The proper way to register and update the DS708 software  is through the DS708 PC suite that you install on a Windows 7 PC. It is all done from the card reader off a PC . I would not turn on the unit's WIFI and allow it to  connect to the internet and Autel's server. Update the new card after you had copied and pasted the original software onto  it and and verified it works. Update the software through the card reader in a Windows 7 PC via the DS708 software suite one car make at a time. Do not click update all or things may get corrupted.