Safety first
Do not turn a detection problem into a data-loss problem.
Microsoft's Disk Management documentation warns that formatting a volume destroys the data on that partition. If this is an existing external drive with files you care about, do not click Initialize, New Simple Volume, or Format merely because Windows offers those options. First determine what state the disk is actually in.
Step 01
Identify the external disk by capacity.
Open Disk Management with Win+R → diskmgmt.msc. Match the external disk by its approximate size. A marketed 2TB drive will appear somewhat smaller in Windows because manufacturers and Windows report capacity differently. Confirm twice before changing anything.
Step 02
If the partition is healthy but has no letter, assign one.
A normal formatted volume can be invisible in File Explorer simply because it has no drive letter. Right-click the existing volume → Change Drive Letter and Paths → Add → choose an unused letter. This does not require formatting the existing volume.
Step 03
Use the displayed state to choose the next action.
Assign a drive letter.
Investigate why it is offline, then bring it online only when you have identified the correct disk.
Do not format if you need the files. The file system is not currently readable by Windows.
Do not create a new volume on a previously used disk until you understand why the partition is missing.
Step 04
Confirm what Windows sees with PowerShell.
Microsoft documents Get-Disk as returning disks visible to the operating system and Get-Volume as returning volume objects. These are read-only checks when used without modification cmdlets.
Get-Disk
Get-Disk | Where-Object BusType -eq 'USB'
Get-VolumeIf the physical USB disk appears in Get-Disk but there is no expected volume in Get-Volume, focus on partition/file-system state rather than USB detection.
Step 05
If it is a new empty drive, treat it differently.
A genuinely new blank disk may need initialization, partition creation, formatting, and a drive letter before File Explorer can use it. Microsoft documents those actions in Disk Management. That is appropriate for a new empty disk — not as a blind repair step for an existing drive containing files.
Decision
When to stop troubleshooting and protect the data.
If the drive contains important files and suddenly appears as RAW, Unallocated, or with a missing partition, stop making write changes. If the drive is also disconnecting, clicking, or failing to stay online, prioritize data recovery or backup rather than “fixing” the partition table.
Sources