I've unlocked several Xbox HDD's by using configmagic to 'generate' a password.
...This doesn't usually work first time, its usually best to let it 'generate' a password several times until it gets to the point of 'generating' one lot of consistent numbers/letters.
...Try it several times just to be sure. I usually have success after trying it twice.
Once u have your password, bung the HDD in a P.C and use 'hdunlock' in DOS.
...Works a treat
If u don't like doing all this the hotswapping is the way to go.
First off, d/l 'xboxhdm' from the usual places and burn a self booting ISO.
...Disconnect your Xbox DVD drive, fire up your Xbox with a P.C running next to it with no HDD's attached.
As soon as u get the error message on the Xbox, unplug the IDE and plug it into the P.C IDE, then allow xboxhdm to detect it and follow instructions.
...Hotswapping is rather crude, but yet again it does work if u r careful and think about what u r doing.