HDD Hitachi Problem

[AntonioLC]

Good morning, I have a problem on which I have exhausted all my analysis skills.
I have an HP Envy 27-b1xx AIO PC with OS Windows 10 Home Version 20H2 Build19042.1083. I have two internal disks, one SSD Samsung MZVPW256HEGL-000H1with the OS and most of the applications on it, the other is a 1TB HDD Hitachi HGST HTS721010A9E630 on which I had installed some applications and all my personal data. Now it happened that a few days ago all the application and personal files disappeared from the Hitachi HD. I've tried to recover the data with Wondershare RecoverIt without success (unreadable files), I've passed a complete analysis with antivirus (no virus found), I've restored Windows 10 conditions to before the last update (June 2021). The current situation is that everything works: OS and operations on the SSD drive, while on the Hitachi HDD drive I can save and read files, but they disappear after a few hours. I reverted to the OS build version described above, the volatility of the files continues.
Can anyone indicate to me what is happening and what should I do to be able to continue using this internal disk as well?
Thanks to those who will give me some indication.

[Prométhée]

Hello
kind of weird
do the tests, it may be defective

HP PCs - Testing for Hardware Failures | HP® Customer Support

If it works
otherwise see the constructor tools if there is

[AntonioLC]

Done! All tests passed! I try to use Hitachi Drive Fitness Test

[Prométhée]

ok i'm waiting for the result
have you tested the disc with another computer to see if there is the same problem? *

[AntonioLC]

Unfortunately, the Hitachi Drive Fitness Test program does not run.

Probably because it is 32-bit?

I couldn't find a 64 version.

The HDD is an internal disk in an all-in-one PC and it is extremely complicated to connect it to another PC.

However, by connecting another Hitachi external HDD to my PC, a different model, the problem of files disappearing does not occur.

[Prométhée · Accepted solution]

If another disk is performing strange that the test is ok, it seems to have a problem

remove whatever is on it if there is still something, format it, completely, then test a few files to see