an error code six means it cant unlock the hard drive right? what are the reasons for this error to happen?

besides not having the proper unlock code

Ihave never seen any other reason for an error code 6. Basicaly it is just like it says. The harddrive is locked & the xbox can't unlock it. either the drive was locked with a different code (as in a different xbox or with a pc based lock utility) or the portion of the eprom where the code is stored has been altered in some way(changed, written to or corupted.)

Hope this helps...