Troubleshoot a missing drive letter for a partition on a Windows instance - Elastic Compute Service

Problem description

Not visible in File Explorer: The disk partition does not appear in This PC or File Explorer.
Normal status in Disk Management: The partition is visible in Disk Management and its status is Healthy. However, the partition is not assigned a drive letter, such as D: or E:, and is not mounted to a folder path.

Causes

Automount is disabled: The system's automount feature for new volumes is disabled. As a result, newly added or created volumes are not automatically assigned a drive letter.
Group Policy restrictions: A Group Policy is configured to hide specified drives in This PC.
Manual removal: The drive letter was manually removed or was not reassigned after an operation such as resizing or formatting the partition.

Solution

First, manually assign a drive letter to the partition. If the drive letter disappears after a restart, check and enable the system's automount feature. Finally, check for any restrictive group policies.

Step 1: Manually assign a drive letter or mount point

Choose one of the following three methods.

Use Disk Management (GUI)

Press the Win+X keyboard shortcut and select Disk Management from the menu.
In the list of disks, find the target partition that does not have a drive letter. Right-click the partition and select Change Drive Letter and Paths.
In the dialog box that appears, click Add.
Select Assign the following drive letter, choose an available letter from the drop-down list, and then click OK.
If the Change Drive Letter and Paths option is grayed out, check if the partition has an abnormal status. Do not assign a drive letter to a system reserved partition.

Use DiskPart (command line)

Open Command Prompt as an administrator.
Run the diskpart command to enter the DiskPart environment.

Run the list volume command to view all volumes. Identify the volume number of the target partition based on its label, size, or other information.

# DISKPART> list volume
#
#  Volume ###  Ltr  Label        Fs     Type        Size     Status     Info
#  ----------  ---  -----------  -----  ----------  -------  ---------  --------
#  Volume 0         SYSTEM_DRV   NTFS   System      260 MB   Healthy    System
#  Volume 1    C    Windows      NTFS   Boot        118 GB   Healthy    Boot
#  Volume 2    D    Apps         NTFS   Partition    50 GB   Healthy
#  Volume 3         Data         NTFS   Partition   100 GB   Healthy    <-- Target partition, no drive letter

Select the target volume.
Replace <volume number> with the volume number of the target partition.
```
select volume <volume number>
```
Assign a drive letter to the selected volume.
Replace <drive letter> with the desired drive letter.
```
assign letter=<drive letter>
```
For example, to assign the drive letter G, run the assign letter=G command.
Run the exit command to quit.

Use PowerShell (command line)

Open PowerShell as an administrator.
View partitions that are not assigned a drive letter.
Note the disk number (DiskNumber) and partition number (PartitionNumber) of the target partition.
```
Get-Partition | Where-Object {$_.DriveLetter -eq $null}
```
Assign a drive letter to the specified partition.
Based on the output from the previous step, replace DiskNumber and PartitionNumber with their actual values, and replace NewDriveLetter with the desired drive letter.
```
# Example: Assign drive letter G to partition 2 on disk 1
Set-Partition -DiskNumber 1 -PartitionNumber 2 -NewDriveLetter G
```

Step 2: Check and enable the automount feature

If the drive letter is lost after each server restart, check if the automount feature is disabled.

Open Command Prompt as an administrator.
Run the diskpart command to enter the DiskPart environment.
Check the automount status.
```
automount
```
If auto-mount is Disabled, enable it.
```
automount enable
```
The success message is: Automatic mounting of new volumes is enabled.
Run the exit command to quit.

Step 3: Check and disable the Group Policy for hiding drives

Press the Win+R keyboard shortcut, enter gpedit.msc, and press Enter to open the Local Group Policy Editor.
Navigate to User Configuration > Administrative Templates > Windows Components > File Explorer.
In the policy list on the right, find and double-click Hide these specified drives in My Computer.
In the configuration window that appears, check the policy status.
If the status is Disabled, you can configure the setting to Not Configured or Disabled to display all drives.
Click OK to save the settings.
To apply the changes immediately, refresh the Group Policy.
Open Command Prompt as an administrator and run the gpupdate /force command.