If you don't know the password then forget it, you need specialist equipment to unlock Hitachi drives.
AFAIK there are no "back door" passwords, or "secret shorting points" or other Mumbo-jumbo for these drives.
As you will see from "hddunlock.com" hitachi is not supported for software unlocking.
It is easily done by a pro with the correct equipment, but expect it will be cheaper just to trash this drive and buy a new one