Just read this on another forum, not sure what to make of it, but it seems legit. I'm not too sure whether it's okay to direct link to the site, so if you just Google "The Null eeprom Trick!!!" it should be the first result. Credit to gilou9999 for posting the tut.
Yeah it's legit, but it's not a new thing, I have posts on other forums with the exact same process & so have others. All my Xbox have a nulled HDD key, serial & all the same online key. This means all saves will work on all Xboxs & all hard drives are swappable. Post from 2014
Surely this is just common sense? You are changing the key to be all zeros, so any hdd locked to all zeros will work if you did the same on another xbox. But more people that know to change the serial and online keys as well to make saves compatible as a standard part of modding the better.
I'd never heard of it until yesterday which is surprising since I've soft modded enough Xbox consoles in the past and always kept a backup of the EEPROM.
Keeping a backup of the EEPROM isn't a bad idea anyways, though with an EEPROM reader you can always read it.
Please, always make a backup of your eeprom. Hell, also from your entire hdd, its only 10gb or less (retail).
I've always just kept the original hard drive from the machine after cloning to a larger (via Chimp) to ensure I have a solid starting point should the new drive ever croak for some reason.