If you are unaware what or how an Auth Key works I suggest visiting XBOX-Saves.com’s Forums for some research.

Syntax: authkeypatch [filename] [ID number] ID Number must be a number from 0 - 65,535

Just run the program on any xbe file and it will patch it to use the same AuthKey and also patch it so it uses a different folder number, depending on the unique ID number you give it. I've made it so you can have up to 65,536 unique folder numbers, which should cover every Xbox game ever made, plus the number should never interfere with any real folder numbers used by any game.

Also, the xbe files will be patched, so that the game will show up in the dashboard memory manager, with the prefix "Non-XBL", so you can tell which saves are from your retail game and which ones are from your patched game. This will let you keep your old retail saves, in case you need them to play on XBL.