Partition keeps disappearing (Windows 10 and 11)

[PinheadBE]

Hi there,

I have a problem with my PC.   It happened with Windows 10 and still does with Win 11

For historical reasons, my drive has a partition named Z: that I use for all my electronics tools, data and projects
Now, every day (not at regular hours) my Disk partition Z: gets unassigned automatically and disk is hidden and I have to go to disk mgmt and assign a drive letter to the disk to show in the windows explorer.
A windows terminal (cmd.exe) pops up for a sec and disappears and then I go to explorer and the drive is hidden.   No instructions appear in the window, as if @echo off was issued.
In disk mgmt, the partition is still there, but with no drive letter assigned.

I look in the Windows log files, and the scheduled tasks, but I don't find anything.   I'm not sure what I must look for anyway.....

Any help would be appreciated

Thanks

[Jeroen3]

Is you disk bad?

https://www.hdsentinel.com/

[xmris]

as above, plus I would check the HDD cables and PSU voltages.

[RoGeorge]

Seems like a malware.  Try changing the assigned letter, and see if it is still happening after that.

[Whales]

You mention a CMD window appearing.  Maybe you have some old .bat or .cmd script somewhere that occasionally steals that drive letter?  Was this computer ever used in a corporate environment that might distribute scripts or use share drives?

Aside: per-user and system-wide drive letter associations might now be different things.  I vaguely recall this at least being a problem with network share drive letter assignments.  Might be worth checking to see if there are entries in both or just one.

[PinheadBE]

Thanks to all,

The disk is not bad, it is my internal HDD, and I already chkdsk it numerous times: it is ok
Not a malware either: my KIS does not detect it, and it happens for years now.

If I'd know where and what to look for in the log files and/or the task scheduler, this could help....

I searched my disks for .bat and .cmd files, but didn't find nothing related to this.
My computer was bought new in box 3 or 4 years ago

[DavidAlfa]

Strange, try Diskpart, the low level utility:

Code: [Select]

List disk
Select disk N
List part
Select part N
Assign letter=Z

[mcinque]

Seems like a malware.

Why a malware should do that?

[DavidAlfa]

Open the Device Manager, click View/Show hidden devices.
Expand USB devices, Disks, Volumes, then delete all the greyed/faded devices with the Del key.
Those are old devices no longer connected, sometimes they get stuck causing this issues.

Running a system integrity is easy:

Code: [Select]

sfc /scannow
If showing errors, it might need several times, rebooting between them.

If still showing errors after at least 3 tries, switch to dism:

Code: [Select]

dism /online /cleanup-image /restorehealth

Might also need several attempts.

[AndyBeez]

My thoughts:

Is the disk marked as a master bootable partition or (correctly) an extended logical partition? Two 'system active boot primary' partitions can conflict.

File system for Z should be NTFS or FAT16/DosFAT.

Check logical partition size is <= extended size.

Indeed, checkout diskpart:

https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/diskpart

[50ShadesOfDirt]

PC bought several years back, and possibly with OS not reinstalled cleanly, may mean some garbage laying around. Some options for you:

1. reinstall OS cleanly, or have it done for you ... this should probably be done every few years anyway just to clean out the deadwood. Implies backup of your data, reinstalling the apps you care about, etc.

2. go through your startup locations (start menu, task mgr, registry), and see if anything was left over from years before.

You can find loads of web pages to help you through #2, and specialized applications that will scan/clean the registry of all the deadwood.

May still need option #1, at some point ...

[m k]

Drive letters are not static.
Drive may have a static letter but its appearance differ depending what happens elsewhere.

Some devices have higher priorities than others.
There higher priority device will "steal" the drive letter.

There are also other, usually older things that can mess with Z: drive.
Like mentioned above, best start is to change that letter.
If there's no drive B: that should be pretty solid.

What kind of a list you get if you try mapping a network drive?

[PinheadBE]

More precisions:

This is not a network drive.   It is a partition, part of a physical internal HDD in my PC

About OS: I switched to Win11 several months ago, but I got the problem already before that

[m k]

It's a drive, physical or logical, no matter, but it's just a name.

Network drive is an "acronym" of a target of a logical operation of mapping.
Physical presence is mostly irrelevant.

Nowadays you can also map a local drive.