Overview #
When an external hard drive powers on but doesn’t appear in File Explorer or Finder, it usually means that your operating system recognizes the hardware but can’t access its partition or file system.
This can happen due to a missing drive letter, corrupted partition, damaged cable, or a file system that your OS doesn’t support.
This guide explains how to identify what’s wrong and restore full access safely—without risking data loss.
What you’ll learn
- How to confirm whether your computer detects the external drive
- How to assign or mount the drive manually
- How to repair or reformat a damaged file system
- How to read and interpret storage health information
Estimated time: 15–30 minutes
Skill level: Beginner to Intermediate
Terms and Definitions #
| Term | Meaning |
|---|---|
| Mount | The process of making a drive accessible by assigning a letter (Windows) or path (macOS) |
| Partition | A defined section of a physical drive that stores data and file structures |
| File System | The structure used to organize and access files (NTFS, exFAT, APFS, HFS+, etc.) |
| SMART Status | Self-monitoring data that reports drive health and potential failure conditions |
| Unallocated space | Disk area not assigned to any partition, invisible to the operating system |
Steps #
Step 1 — Confirm Power and Cable Function #
- Plug the drive directly into a main USB port on your computer (avoid hubs).
- If the drive uses an external power supply, make sure it’s plugged in and the LED indicator lights up.
- Try a different USB cable and another USB port to rule out bad connections.
- If possible, test the drive on another computer to confirm it powers on and spins normally.
If the drive isn’t detected at all, replace the cable or power adapter before proceeding.
Step 2 — Check Drive Detection #
Windows PowerShell
Get-Disk
Lists all physical disks detected by Windows.
If your drive appears here but isn’t assigned a letter, it’s recognized at the hardware level but not mounted.
macOS Terminal
diskutil list
Displays all connected drives and their partitions.
If you see your external drive listed but not mounted, continue to the next step.
Step 3 — Mount or Assign the Drive #
Windows
- Right-click the Start menu → Disk Management.
- Find the external drive in the list.
- If it’s marked Offline, right-click → Online.
- If it shows No Drive Letter, right-click → Change Drive Letter and Paths → Add.
- Assign a letter (e.g., “E”) → OK.
macOS
diskutil mountDisk /dev/disk2
Replace /dev/disk2 with your drive’s identifier from the previous command.
If the system reports that the disk “cannot be mounted,” the file system may need repair.
Step 4 — Verify File System Integrity #
Windows
chkdsk E: /f
Replaces “E:” with your drive letter. This checks and fixes file system errors.
If you see “RAW” instead of a format like “NTFS” or “exFAT,” the partition table is damaged.
macOS
diskutil verifyDisk /dev/disk2
diskutil repairDisk /dev/disk2
Checks and repairs drive structure issues.
If repair fails, data recovery tools may be needed before reformatting.
Step 5 — Initialize or Rebuild the Partition Table (Advanced) #
If your drive appears as Unallocated or Not Initialized, the partition table may be missing or corrupt.
Windows
Initialize-Disk -Number 1 -PartitionStyle GPT
New-Partition -DiskNumber 1 -UseMaximumSize -AssignDriveLetter | Format-Volume -FileSystem NTFS -NewFileSystemLabel "ExternalDrive"
Use this only if you have already recovered your data or the drive is empty—it reformats the disk.
macOS
diskutil eraseDisk APFS "ExternalDrive" /dev/disk2
Erases and reformats the disk using Apple’s APFS format.
Choose “exFAT” instead of “APFS” if you want cross-compatibility with Windows.
Step 6 — Review System Logs for Disk Errors #
Windows PowerShell
Get-WinEvent -LogName System | Where-Object {$_.Message -like "*disk*"} | Select-Object TimeCreated, Message -First 15
Displays recent disk-related warnings or errors.
macOS
log show --predicate 'eventMessage CONTAINS "disk"' --last 1h
Shows any errors or mounting attempts logged in the past hour.
This helps confirm whether the system tried and failed to read the drive.
Step 7 — Check Drive Health (SMART Status) #
Windows PowerShell
Get-PhysicalDisk | Select-Object FriendlyName, HealthStatus, OperationalStatus
HealthStatus should read Healthy or OK.
macOS
diskutil info /dev/disk2 | grep SMART
A “Verified” status indicates no imminent failure.
If you see “Failing” or “Not Supported,” back up data immediately and plan to replace the drive.
Step 8 — Test on Another Computer or OS #
If the drive mounts on another system but not yours:
- Update your USB and chipset drivers (Windows).
- Reset NVRAM/SMC (Mac).
If it fails on every computer, the enclosure’s controller board or the internal drive may be failing.
You can test by removing the bare drive and connecting it via a USB-to-SATA adapter.
Verification #
| Check | Command | Expected Result |
|---|---|---|
| Drive visibility | Get-Disk / diskutil list | Drive listed with correct size |
| Mount status | diskutil info | “Mounted: Yes” |
| File system | chkdsk / diskutil verifyDisk | No reported errors |
| SMART health | Get-PhysicalDisk / diskutil info | “Healthy” or “Verified” |
After confirming these checks, verify you can read and write files normally.
Conclusion #
When an external drive is detected but not visible in File Explorer or Finder, the issue usually lies in the partition table, drive letter assignment, or file system structure.
By systematically checking detection, mounting, and health, you can restore access without reformatting unnecessarily.
If the drive repeatedly disconnects or shows failing SMART data, back up your files immediately and replace the device before complete failure occurs.
