Windows 10: Internal HDD not showing in Explorer, shows in DiskMgmt as Unallocated

Booted up from sleep this morning after using the PC fine last night, only to discover that my partition of one of my Seagate drives had vanished from Explorer.

Checked Disk Management and it is showing up in there and registers as 'Online' however all the space is now marked as 'Unallocated'
Shows up on BIOS boot fine so it's connected and can be seen. Also doesn't show up normally in Safe Mode.

It's a 2TB HDD, so will likely take hours to scan using recovery software.
Anything I can do or are my files gone?

:)

 

Seagate 3TB shows 128GB unallocated memory!

So i've just bought a Seagate 3TB internal hdd (having an 4TB Boot drive already).
But in the Disk management it shows 128GB unallocated memory and its greyed out!
What can i do now?
Any help will b appreciated!

 

USB3.0 Issues and Internal HDD shows as removable


Update: So I went to BIOS settings and disabled all Hot Swaps.... here's what's worrying me
1. The HDD is not even listed as one of the connected devices!!
2. Other SSD's do appear.
3. The issue still persists. The internal drive shows under Portable Devices.

 

HDD not showing in the File explorer in Windows 10.

Hello Lorna,

Thank you for posting on Microsoft Community. We will assist you in resolving the issue.

Unallocated drives are those whose drive letters are not allocated. You will be able to view the drive on your PC if you have allocated a drive name for the partition created. The drive will not be visible on the PC if you do not allocate a drive letter
or a drive name.

Allocate a drive letter to the HDD by following the steps below and check if the issue is resolved.

• 
  Connect the HDD to the PC.
  
• 
  Open Run command by pressing
  Windows Key + R keys on the keyboard, type diskmgmt.msc and press
  Enter.
  
• 
  Right click on the Unallocated disk drive and select
  New Simple Volume option. Follow the onscreen instructions where in the process you will get to a window where you can allocate a drive name for the HDD.
  
• 
  After allocating a drive letter, right click on the drive and select
  Open. Check if you are able to open the drive in File Explorer.
  

Write to us with the status of the issue on the same post for further assistance. Your reply is most important for us to ensure we assist you accordingly.

Thank you.