There are different ways to flash your NEC DVD burner at the moment. For DOS, Windows commandline and GUI, Linux and Mac you can use Binflash while TDB have software for DOS and Windows GUI. Be sure to always download the latest versions of these programs directly from the author's sites before flashing your drive.
If you are working with Linux or Mac, you will probably have to use the commandline versions of Binflash.
Before flashing your drive, remember to always backup the current firmware and make sure that the one you want to flash is compatible with your drive.
How to use the commandline version of Binflash
How to use the GUI version of Binflash
How to use TDB's DOS flasher