It can't be removed once lost without the assistance of a data recovery service with the software necessary to access the user-inaccessible portion of the drive. The other issue is more pressing:  you will need to contact Dell support and verify your ownership of the system before you can have the BIOS-based password removed.  That must be removed in order to replace the drive, or the next drive will inherit the unknown password. Once that's done, if you do not need the data on the drive, the least expensive way to proceed is to replace the drive.  If you do need the data, you'll need to send the drive off to a data recovery service to have the password removed.  That will undoubtedly cost more than a replacement drive.
I forgot my HDD password and now the laptop isn't getting started without HDD password being entered. How to remove HDD password? [IMAGE]
HDD password, #2