USB external drive letter not remembered

Hi Art — in Windows, a drive letter you set in Disk Management is normally persistent, but it’s only persistent as long as Windows keeps seeing the same volume identity and the letter is available. When it suddenly comes back as H:, it’s usually one of these:

• N: is no longer free (often because a mapped network drive, SUBST drive, or another device grabbed it).
• Windows is seeing the external drive as a “different” device/volume than before (different USB port/controller, flaky enclosure/USB bridge changing its ID, partition changes, etc.).
• The Windows mount manager database got confused/corrupted and is re-assigning letters.

Below are the best fixes, in order.

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1) First check if N: is being taken by something else​

A. Check mapped network drives​

Open Command Prompt and run:
net use
If you see N: listed, delete it:
net use N: /delete

B. Check for SUBST drives​

subst
If N: is listed there:
subst N: /d

C. Quick PowerShell view of “who has what”​

Open PowerShell:
Get-PSDrive -PSProvider FileSystem
If N: is already in use at the moment you plug the USB drive in, Windows will assign the external drive the “next available” letter (often making it look random).

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2) Re-assign the letter using DiskPart (often “sticks” better than the GUI)​

1. Plug in the external drive
2. Open Terminal (Admin) (or Command Prompt Admin)
3. Run:

Make sure you select the correct volume (match by size/label).

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3) Verify AutoMount is enabled (this controls persistent letter behavior)​

In Terminal (Admin):

• If it says disabled, enable it:
  
  Code:

  automount enable
  exit

You can also force-enable mount manager behavior with:
mountvol /E
Reboot once after changing AutoMount.

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4) Important: always use the same USB port (at least to test)​

On some systems, plugging into a different physical port (especially switching between USB-A vs USB-C, front-panel vs rear, dock vs direct) can cause Windows/enclosure to present the drive differently, and the letter assignment can “drift”.
Try using the same port consistently for a few plug/unplug cycles and see if it stays N:.

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5) If it still won’t remember: rebuild the mount manager database (safe, but do it carefully)​

This can fix cases where Windows’ stored mappings got messy.

1. Unplug the external drive
2. Terminal (Admin):
   mountvol /R
3. Reboot Windows
4. Plug the drive back in and assign N: again (Disk Management or DiskPart)

Note: This can cause Windows to “re-discover” mount points for removable storage, so don’t be surprised if some other removable device letters get re-evaluated.

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Quick questions (these pinpoint the cause fast)​

1) When the USB drive shows up as H:, is N: already visible in File Explorer as some other drive (network share, etc.)?
2) Do you ever use VPN / corporate shares / logon scripts that map drive letters?
3) Are you plugging the drive into the same USB port each time?
If you paste the output of:

• net use
• subst
• Get-PSDrive -PSProvider FileSystem

…I can tell you immediately if something is stealing N:.