Windows 10 1803 Update Creates an Additional OEM Partition

Users have noticed that when upgrading to Windows 10 1803 (April 2018 Update), a separate additional OEM (recovery) partition appears on the local drive. This partition is assigned a separate drive letter, it is displayed in File Explorer and in the Disk Manager snap-in. The size of the additional OEM partition with the NTFS is about 450 – 500 MB. However, there is not enough free space on this volume, less than 9%. As a result, Windows 10 starts constantly displaying notifications that this disk is almost full.

I’ll try to explain briefly for which this partition is used, and whether you can delete it or just remove annoying notifications.

On the new OEM partition, only the Recovery and System Volume Information folders are present.

If you run the command reagent /info, you can verify that the new OEM partition is used to store boot image of the Windows Recovery Environment (WinRE). Why the developers of Windows 10 decided to move the image of the partition to a separate disk is not clear.

If you want to save the ability to restore the system using WinRe, you do not have to delete this partition (using the article How to remove the OEM partition in Windows). However, it’s completely safe to just remove the drive letter from this partition. On WinRE this will not affect, because as the path to the image of Winre.wim is used the address in the format \\?\GLOBALROOT\device\harddisk0\partition5\Recovery\WindowsRE (as you can see, the path does not contain the drive letter).

You can hide an extra OEM partition this ways:

1. You can delete the drive letter assigned to it via Disk Manager (diskmgmt.msc). Right click on the OEM partition -> Change drive letter and paths -> Remove. In this case, the volume will simply stop displaying in the File Explorer, but it will not be deleted from the HDD. You can’t remove this additional partition from the Disk Manager console (the delete button is inactive).
2. It is even easier to remove the mount point of the disk using the following command that is run on the command prompt with administrator privileges: mountvol E: /D
3. You can also remove the drive letter on this partition with the diskpart command, but this is a little more complicated. To delete a drive letter, you need to use the following commands:
   diskpart
list volume
select volume <volume_number>
remove letter=<drive_letter>
exit

That’s all, you hide the new OEM partition from the user, and there are no more notifications about the end of disk space.