Unlocking a HDD without password can be done :
1) Download liveinfo-beta2
2) Power up your pc and boot into windows (only done with xp so far)
3) Plug the IDE cable onto the XBOX HDD
4) Plug a pc power lead onto the XBOX HDD
5) Open device manager and scan for hardware changes, you may need to do this a couple of times, and it sometimes looks like device manager has crashed (can be as long as 5 mins) but the device will appear eventually, No other part of windows will see it !!
6) Run Live info and retrieve the password
7) Unlock as normal
I do not guarentee this method, all I know is it has worked for me, liveinfo reports that the drive is lockable, is actually locked, and tells you the password