Windows just Trashed 1TB data External HDD

Ownership goes by Sid security identifier so when on seven it's would be owned by the user of that windows with a number which is what your seeing as a missing account the name may be the same in ten but the numbers will be different and if you logged into ten with a ms account it would be different again

Hi aramil,
Bad Drive is remote possibility.
I am always using "Eject Drive" and only remove it says is "Safe to remove it".
I think, I have no chance to recover Data, CHKDSK already removed all references to Data, all I have is garbage.
I will erase and Initialize the Drive again, but before I will wait a little until an "Expert" says something about recovering possibilities.

The problem is recurrent, (see link above) and is known to happen.
I think the Key problem is changing the Ownership to something else.
How can it be that suddenly the Drive Ownership is changing and worst to a "Unknown Account". Where from is coming this?
I think that is a serious Bug, it is a simple way to Lock/Destroy HDD. Scaring is that you never know when it will happen.

Samuria said:

Ownership goes by Sid security identifier so when on seven it's would be owned by the user of that windows with a number which is what your seeing as a missing account the name may be the same in ten but the numbers will be different and if you logged into ten with a ms account it would be different again

Well, the thing is the HDD Ownership was changed , I was getting the message "Access Denied". I was Logged In System with my only User Account, HDD was working Normally and accessible and suddenly it Changed, who knows why?

aramil said:

You are confusing two issues, the example you link to is a permissions error with one system OS level event (chkdsk win10) trying to modify another system level's main OS drive (win 7) , the user did not loose the data just access to it, which was restored.

The Unknown account is your old win8.1 SID as @Samuria posted above, it is machine & user & OS dependent (not just account), if this (user) really was the cause, every time someone used a usb drive to transfer data between computers the second computer would chkdsk and wipe the drives data, which i am sure the internet would of exploded about.

Yours is a data corruption issue that has nothing to do with SID's. You have access to the drive and data, but it was returning errors.

The lesson as always stated is have a backup plan for any data you do not want to loose and make sure it is updated on a regular basis.

Thank you aramil,

Immediately after, I have seen that in Explorer and I knew at once I had problems, I tried to run "Scan and Fix" the Drive became as if it was unformated with "Access Denied" as with the other user.
It means the "Onwership" has been changed, why? Why it changed so that it Blocking the access?

Well, Data Corruption, no HDD Defective, who is the Culprit? And a Repair that was not able to Retrieve Data.
It might be, that First NTFS table was bad, but the Second NTFS Table was Worst. So far I recall, it was retrieving files that I deleted one Year ago and for sure, the Data has been overwritten several times, so the recovered Files are garbage.
I think everything is scrambled in HDD, so I have no chance to retrieve Files. I will not spent 100 bucks to get Garbage back.
This is a Super MCA.

This HDD was a Backup HDD and I was using it seldom. I have to think well about Security of my Data , if every time I connect a Drive it gets corrupted, I do better buy 1000 HDD, connect them once and never again, just because.

This happened yesterday, I was so Down and Depressive, I stop working, I had no Head to think not even come here and expose the situation, I am still down, disappointed with all Modern Computing that in Seconds you can lose all data.
Why did I Upgrade, is the question I am doing now?

Hi Slatybart,
Thank you for the Links, I will try them.
I can not imagine that there is something wrong with HDD, so I am tending something went wrong with Security/Ownership.
Anyway I am not expertise on new Windows Features, but I have long experience with PC.

About Disk Management, I just formatted the Partition where Upgrade Win 10 was, now I am restoring Win 8.1 from an older System Image.
Is it enough to open native Windows Disk Management? Or do I need to use the one you said?
I have 2 PC, you mainly want to see the "bad" HDD or the Whole system of the PC where Win 10 was installed?
Thank you.

Here die Disk Management image. The "bad" Disk is Disk 1 or the one just above Drive C in upper pane.