On a notebook system, there are two parts to the hard drive password.
There's a firmware issue, which can only be cleared by Dell support on verification of ownership.
The rest is a drive issue - if there's a password on the drive you've lost, and you need the data, you will need to contact a data recovery service that can remove the password (it's not user-accessible). And clearing the system hard drive password does not change the drive password.
Note: installing another drive in the same system without clearing the firmware portion of the password will result in another locked drive.