To use this generator, you need one of the following:
From the dumped EEPROM, you should have the HDD key. It is in the "xbox info.txt" file that comes with a dumped EEPROM from a Softmodded XBOX.
If you have an EEPROM.bin, then use the Original XBOX EEPROM Editor and use the HDD key there on this page.
If you'd rather not softmod your XBOX, you may use the Insignia LIVE installer to grab the HDD key.
Copy and paste the HDD key (not the HDD password) into the textbox in the generator.
This should spit out a 4 letter code followed by Y. Buttons list as follows:
This should be all you need to know.