Upgrading NEC ND-3520A Dual Layer Support
For the NEC ND-3520A drive if a customer wants to be able to write to DVD-R DL (double layer) discs then they’ll need to flash the drive to support this format. The drives we sell only come with native DVD+L DL support.

Here is the link to the update: http://support.necsam.com/OEM/downloads/FlashFirmware/