You will need a key code that unlocks your locked Xbox HD and the Evolution-X program.
The OEM bios generates the unlock key “on the fly”. That is it generates a unique key or password which is dependant upon several things.
This password is generated by looking at your Xbox’s unique serial number, configuration, revision level and the information obtained from your hard drive itself.
This in turn means that you cannot simply use a password from another drive or Xbox to unlock your hard drive. Instead you must figure out what the Xbox is going to use as an unlock password for your new replacement drive. Fortunately the Evolution-X hackers have made a wonderful tool to do this thing.
This “tool” is built into the Evolution-X dashboards “backup” command. The “backup” command figures out what password the Xbox will use to unlock the drive. It places the password/key into the C:\Backup directory in a file called hddinfo.txt.
This is why Evolution-X must be installed and running on the Xbox and drive that you intend to lock first.
For more info about unlocking you Xbox hard disk read here