Today, I decided to reinstall grub from an Ubuntu LiveCD to see if that was the problem, but before booting from cd my laptop asks for "Hard Disk User Password" which I have never set.
Trying to boot UBCD, does the same.
And what happens if you try again booting from HDD instead of booting from CD? Do you receive the same "Hard Disk User Password" "error"? What about Super Grub Disk and Super Grub2 Disk?
I unplugged the HDD and it doesn't even try to boot, maybe the system somehow doesn't allow the machine to boot without a HDD.
That may be because boot settings in BIOS? What do you mean with "doesn't allow
the machine to boot"? What do you see that points to that conclusion? Was there any CD or UFD inserted? What boot order is set in the BIOS? Was anything else plugged-in to the laptop while trying to boot?
These are points that you should recheck and retest.
So, I have a laptop with only access to BIOS and the screen asking for Hard Disk User Password.
The question is : which are the tools of UBCD that are known for locking the HDD?
If any of these tools has a standard password please share it to give it a try?
Have you searched the forum for similar problems? Can you provide with exact
model info (HDD and laptop)? Have you searched for similar problems at the respective websites of the HDD and laptop's manufacturers? Or maybe at Ubuntu's forum?