I have put a password and a master password on HDD from BIOS. I exit BIOS without saving but it seems like the password was added. So now even when I type the password (and master) that I typed on BIOS, it doesn't accept them, its like its wrong even though i remember well that it was what i typed in. The files inside the HDD are important so I dont wanna just change drive or wipe/format it.

Not gonna work
Perhaps you should try it first on this model, before you suggest sending this drive to you?

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SAN, NAS, RAID, Server, and HDD Data Recovery.

Sediv doesn't support this drive, i already tried with it.
Neither MRT.

Both tools are only able to read ROM and NVRAM, that's all.
I've one of this drives right here (good working drive), i will post a video to show you.

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My firmware database:
https://mega.nz/folder/O01DkBRI

FWIW, the OP's model is HTS721010A9E630. There is a SED version -- HTS721010A9E631. Could that be a clue?

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A backup a day keeps DR away.

Yes

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SAN, NAS, RAID, Server, and HDD Data Recovery.

Did you compare the SECI modules of two unlocked drives? If so, were they unique?

What about SECB? Is it relevant?

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A backup a day keeps DR away.

I might be at help...contact me through my website or Pm me.

Bosse

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Rescue IT Datarecovery service Sweden
Rescue IT Dataräddning Göteborg AB
http://www.rescue-it.se

Unfortunally sediv isn't even able to backup NVRAM of this kind of drive, at least i can save ROM and NVRAM by using MRT.

Watch the video i made:
https://youtu.be/9HDrgHs80K0

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My firmware database:
https://mega.nz/folder/O01DkBRI

The thing is, I'm 100% sure I had put the same password in all 3 (BIOS, HDD user password and HDD master password), does it automatically change into something else maybe and doesnt accept the same password? When I was opening laptop, it was asking for password, I tried it on HDD normal and master password, nothing, it was saying it was wrong. When i removed HDD, BIOS asked for its password, which it got accepted. So even though I had the same password in all 3, only the bios one accepted it. I even tried with capital letters etc but still nothing works on HDD. I inserted the HDD on a working PC (Windows) with an existing OS, I heard the sound that it got inserted (I even could see it from the safe removal thingy) however at the "My PC" my locked HDD wasn't shown.

What make and model laptop did you use to set the passwords? Did you do it from the bios setup window?
Often the password you type in is hashed in which case the password stored on the drive will be different.

At this point it would be a good idea to confirm the drive is locked using Mhdd or similar.

So back to the make and model laptop......sometimes it is possible to generate an unlock password. Only on a few models though.

I think Victoria is the right tool for him.
http://www.hddoracle.com/viewtopic.php?f=117&t=1072

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My firmware database:
https://mega.nz/folder/O01DkBRI

Make? Model is Asus. All the 3 passwords, I set passwords from Bios, from the security tab.

donddiia, you may try to edit the head map in NV-RAM on unscrewed PCB. Then edit the SECI password module. Thus you would probably get the full SA and data access. I saw this method somewhere on Ace lab blog.

Obviously

In this case it would probably be better to contact one of the local DR companies.