This tutorial will 100% fix your NAND no matter what's wrong with it. Just remember to Create a Freeboot Image after fixing your NAND, or it will f*** up your system, and you will need to Re-flash all over again. <^Important! )
-Your CPU Key
-A NAND with it's CPU KEY - With the same Motherboard Division as the NAND your trying to fix. (Ask you nice friends to borrow theirs)
Open up Bincrypt click 'Raw Flash Bin' and then click 'Extract' now Copy the Donors CPU Key and paste it in the CPU Key field. Make sure 'Keyvault' is selected under 'Supported files'.
Click the spoiler for help.
Click to View Content
Now go ahead and click 'Process' a new window will pop up, now find the Donor NAND and double click on it, it should save the extracted Keyvault. Go ahead and do the same to all the 'Supported files' when you reach 'Config Blocks' it will automatically hop down to 'Nothing' in the 'Operation' tap, don't worry that's normal
When everything's extracted, go ahead and click 'Replace' under the Source field, then go back on 'Keyvault' and click 'ecrypt' on the Operation field, then copy your own CPU Key, and paste it in the CPU Key field. Now you can go ahead and click Process again and do almost as you did before except this time you click the Donor NAND and a new window will pop up and ask for the desired file you have chosen
When everything's decrypted, your done and it should now work as your NAND - To make sure it works go into Xbox 360 Flash Tool and open the NAND that you just created, then go to 'Keys' and insert the CPU Key, now it will start up a new window, and your just gonna open your NAND once again, if you can see all information to the right and it does not say 'Bad KV' then you know that you successfully recovered your broken NAND.