If you have the Cartridge, just re-load the factory presets into the internal memory by pressing Edit, then button 14, scroll along to internal and cartridge memory protect and turn it to off using the yes/no key. Then press buttons 15 + 16, find "Load Cartridge", then press yes. I hope this works as i am assuming that you have the same model as I do.
Duncan
email:- dwmusic@enta.net
PS: I have loads of DX7 sounds on Atari/PC disk if you're interested.