USB drive not detected in Windows: safe diagnosis

Goal If a USB drive is absent from Explorer or diskpart, separate hardware detection from partition and drive-letter issues.

Requirements

Local administrator access
A backup when possible
A second USB port or computer for comparison

Check device detection

If the device is absent here, assigning a drive letter cannot fix it.

Get-PnpDevice -PresentOnly |
Where-Object {$_.Class -in 'DiskDrive','USB'} |
Select-Object Status,Class,FriendlyName,InstanceId

Inspect disks and partitions

Look for offline, read-only or letterless volumes.

Get-Disk | Format-Table Number,FriendlyName,OperationalStatus,PartitionStyle,Size
Get-Partition | Format-Table DiskNumber,PartitionNumber,DriveLetter,Type,Size

Assign a drive letter

Replace the placeholders only after positively identifying the correct disk and partition.

Get-Partition -DiskNumber <DISK_NO> -PartitionNumber <PARTITION_NO> |
Set-Partition -NewDriveLetter E

Caution

Initialize-Disk, Clear-Disk, clean and format can destroy data and are intentionally excluded.