Remove drive letter for SYSTEM partition --- it appeared after Microsoft support request 70<***removed PII***>

Question

The support request number for this issue is 70<removed PII>.

During Quick Assist sessions during the week of February 15, 2026, Microsoft Support agents reinstalled Windows in my Lenovo ThinkPad twice --- first as a complete reinstallation, which wiped all of my installed applications and configurations, then as a repair installation (why was this not done first?), which left my newly reinstalled (quickly after the first, complete installation) applications and configurations in place.

After the problem --- Windows Update failed for the releases in January and February --- was finally corrected, a new drive began appearing in "This PC", drive E:, and a new partition appeared on the system SSD --- probably a disk recovery (?) partition. See below for details on the disk organization.

I would like to see the disk partitions and drive letters restored to the original configuration, before the Windows reinstallation, if possible. At least I would like to remove the letter E from the partition currently assigned that drive letter, so that it no longer appears in File Explorer ("This PC" window image attached).

From information taken from Disk Management, diskpart, get-partition, and regedit, I believe that the drive letter E has been assigned to the SYSTEM partition --- Disk 0, partition 1 (image attached) --- even though the drive letter does not show in Disk Management (image attached), and that the new partition (a second disk recovery partition?) is partition 5.

Right-clicking Disk 0 partition 1 in the Disk Management screen shows the "Change drive letter" option "grayed out", even when running Disk Management as Administrator.

In the registry at Computer\HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices is \DosDevices\E: (image attached).

Can I delete that item?

Will you be able to assist with this overall cleanup and completion of Microsoft agents' support effort?

Answer 1

Hi PT Vernier ,

I have reviewed the issue where an unexpected E: drive is appearing in This PC after the recent Windows reinstall/repair.

This E: drive is not a data drive. It corresponds to a system / EFI or recovery partition, which should normally remain hidden. During Windows reinstall or repair, Windows may temporarily assign a drive letter to this partition.

To safely resolve this, please follow the steps below:

1. Open Command Prompt as Administrator.
2. Run the following command:

mountvol E: /d

1. Then run:

mountvol /R

1. Restart the computer.

After reboot, the E: drive should no longer appear in File Explorer.

If the drive letter reappears, the cause is a leftover registry mapping from the reinstall process. In that case:

• Back up the registry.
• Open Registry Editor and go to:

HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

• Delete only the entry \DosDevices\E:.
• Restart the computer again.

These steps do not affect system boot or user data. They simply restore normal Windows behavior by hiding system partitions.

I hope the information above is helpful. If you have any further questions, please feel free to let us know.

If this answer was helpful, please click Accept Answer and Upvote to help others in the community.

Best regards,
Nam

Answer 2

Hi PT Vernier,

I’ve looked into the issue where an unexpected E: drive is showing up in File Explorer after the recent Windows reinstall or repair. This drive isn’t a normal data volume; it’s actually a system partition (EFI or recovery) that Windows normally keeps hidden. During a reinstall or repair, Windows can mistakenly assign a drive letter to it, which is why you’re seeing it now.

To correct this safely, open Command Prompt with administrative rights and run:

mountvol E: /d

followed by:

mountvol /R

Then restart the computer. After reboot, the E: drive should no longer appear.

If the drive letter comes back, it means the reinstall left behind a registry mapping. In that case, back up the registry, open Registry Editor, and navigate to:

HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

Delete only the entry named \DosDevices\E: and restart again.

These steps won’t affect boot or user data; they simply restore the normal behavior where system partitions remain hidden.

I hope you've found something useful here. If it helps you get more insight into the issue, it's appreciated to accept the answer. Should you have more questions, feel free to leave a message. Have a nice day!

Domic Vo.