Windows 10 Upgrade Hard Drive Partition Lost

I had a 3TB hard drive with a 2TB partition and an 1TB partition. When I upgraded to Windows 10 today, the 1TB partition disappeared entirely. It appears as unallocated in Disk Management, and there are no options to perform any action with it.
I got here through a Microsoft Support question titled “Windows 10 missing disk partition” where the moderator suggested posting the problem here.
My main two goals here are:
1) Getting the data back. I have most of the lost data on another computer, but if I can find it on the disk somehow, it’d save me a lot of time transferring stuff.
2) Getting that space back. Windows won’t let me do anything with that unallocated section of the hard drive, so my hard drive is currently 33% useless.
I’m doing a full scan right now with a third-party tool called Partition Find and Mount, but even if that finds the data, it won’t solve the unallocated space issue.
According to the description in the question, my understanding is that 1TB hard drive has been displayed as unallocated space after upgrading to Windows 10. That seems strange but this is a commonly asked question on each forum.
How to get the lost Windows 10 partition back? In general, third-party recovery tool might be helpful for similar problems, such as Partition Wizard Free Edition and so on.
Step 1: Launch MiniTool Partition Wizard and enter into the main interface.
Step 2: Click on “Partition Recovery Wizard” and choose the disk that lost partition after Windows upgrading.
Step 3: Set scanning range for data recover. Here I choose the full disk. Click “Next” to go on.
Step 4: Quick scan the hard drive if the lost partitions are continuous, otherwise choose full scan.
Step 5: Remember to tick all partition found on this drive and press “Finish” to go back to the main interface. Finally, press “Apply” to make all changes effective.
This is the end of how to recover lost partitions after upgrading to Windows 10. If you are troubled by this issue, try this freeware and check whether it is useful.
Download MiniTool Partition Wizard free edition.
See more features of MiniTool Partition Wizard.


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