Symptoms
- Drive is listed in Disk Management but absent from File Explorer
- Drive letter disappeared after a Windows update or driver change
- Multiple drives are competing for the same letter
- Newly installed second drive isn't showing up anywhere
Likely causes
- CommonNo drive letter was ever assignedNew drives, especially second internal drives, don't always get a letter automatically.
- CommonDrive letter conflict with a network drive or removable deviceWindows may skip assigning a letter if it thinks one is taken.
- PossibleA Windows update reset drive letter assignmentsThis is uncommon but can happen after major updates.
- PossibleThe partition itself is corrupted or unformattedNo letter will show if there's no valid file system to mount.
What to do
- Open Disk Management (search 'diskmgmt.msc' from the Start menu).
- Find the drive by its size in the list at the bottom.
- Right-click the partition and select 'Change Drive Letter and Paths'.
- Click Add, choose an unused letter, and confirm.
- If the partition shows as unallocated instead of a normal partition, don't format it yet if you expect data on it.
- If it's truly a new, blank drive, right-click and choose 'New Simple Volume' to format and assign a letter.
When to call a pro
If the partition shows as unallocated and you expected existing data, stop and get recovery help before creating a new volume.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.