External drive missing in Explorer: add a missing drive letter
What to do first
Use this procedure when an existing healthy data volume needs a letter. Identify it carefully before making a change, and stop if its state indicates a different problem.
This is a general troubleshooting guide, not an announcement of a current outage.
Affected products and symptoms
- Product
- Windows
- Versions and conditions
- Windows 11 / Windows 10; healthy data volumes without a drive letter
Symptoms
- An external SSD or hard drive is absent from This PC
- Disk Management shows a healthy volume without a letter
Causes and conditions
A healthy data volume without an assigned letter may be missing from the usual Explorer drive list. RAW or unallocated storage requires a different diagnosis.
Before you start
- Note the device capacity, model and previous volume label
- Use an administrator account and pause writes to the external drive
Precautions
- Do not delete partitions or initialize the disk
- Do not assign letters to Windows, EFI or recovery volumes
Tools and official pages used in this guide
Step-by-step instructions
Open This PC in File Explorer and check the drive list. A USB connection sound alone does not confirm that a usable volume is available; check enclosure power and cabling.
A disconnected network share or access-denied error on a drive that already has a letter does not match this procedure.
This procedure applies only to a recognizable healthy data volume missing a letter. A device absent from Disk Management, an uninitialized disk or an inaccessible lettered volume requires another branch. Record identity, capacity, filesystem, state and letter; a USB sound is not proof of storage recognition.
Search Start for Computer Management, open it as administrator, then select Storage > Disk Management. Match the device using its capacity and volume label.
If it is missing, try Action > Rescan Disks once. When several devices have similar capacities, establish which is yours before selecting a volume.
Distinguish the disk number from its individual partitions. Identify the needed data volume through names and connection information rather than similar capacities. Safely removing unrelated external devices can help identification, but do not unplug writing devices or an active storage pool for diagnosis.
Official links for this step
Add a letter to a healthy unlettered data volume; preserve data for RAW/unallocated states; inspect power and connections for an absent device. Record state before branching. Recreating a formerly populated partition is not a missing-letter repair.
Continue only for the existing healthy data volume with a recognized file system and no letter. Exclude Windows, application, EFI and recovery volumes.
Stop if storage that should contain files appears RAW, unallocated or uninitialized. Initializing, formatting and creating a new volume are not letter-assignment operations.
Right-click the target volume and choose Change Drive Letter and Paths, then Add. Select an unused letter under Assign the following drive letter and confirm.
If the option is unavailable, recheck the volume state and permissions. Do not substitute a different disk operation to force it through.
Check mapped drives and expected application paths before choosing an unused letter. Adding a missing letter differs from changing an existing one, which can affect backups and shortcuts. For unavailable controls, inspect volume selection and privileges without replacing the operation with initialization, deletion or new-volume creation.
Official links for this step
Once readable, verify intended paths in backup and application settings. Retest the same volume after reconnection. Record a changed letter rather than assigning it to another disk to conceal the mismatch.
Reopen This PC, open the assigned drive and look for known folders. Read a small existing file and check its contents.
Once accessible, copy important files to another destination. Copy errors or disconnects mean that assigning a letter has not resolved the remaining storage problem.
Read known folders and a small existing file after addition. An empty volume may be the wrong target. Separate letter assignment from permissions or encryption access. Copy important files to independent storage and open the copies. For disconnects, very slow reads or unusual noise, decide on recovery before repeated operations.
Check the result
- The assigned drive appears and existing files open
- Important files copy successfully and can be checked at the destination
- The identified healthy volume receives a letter and known existing files are readable
If the problem continues
- For RAW or unallocated storage containing needed data, stop writes and seek recovery advice
- If Disk Management cannot see the device, investigate its connection, power and hardware
Scope of this guide
Troubleshooting guide — The identified healthy volume receives a letter and known existing files are readable
Frequently asked questions
Should I accept a format prompt?
Stop if you need existing data. Record the volume state because the problem may extend beyond a missing letter.
Does assigning a letter move the files?
Adding a letter to an existing healthy volume does not copy or move its files. Identify the correct volume first.
Will adding a letter make a RAW volume readable?
A letter does not repair a filesystem. If required data appears as RAW, stop writes and record state and prior actions. Decide on data recovery before following a format prompt.
Official sources and dates
- Change a drive letter ↗
- Troubleshoot Disk Management ↗
- Move your files to a new Windows PC using an external storage device ↗
Source publication or resolution date: 2025-06-26. Sources checked: 2026-10-13. The check date is not the date the problem first occurred. Interface labels can vary between versions and display languages.
Related troubleshooting guides
Windows errors and troubleshooting →