After installing the Windows 10 April 2018 Update (version 1803), one or more drive partitions that would normally be hidden may be assigned a drive letter and appear in File Explorer and Disk Management. These partitions are typically between 400 MB to 1 GB and contain important info used by the Windows Recovery Environment (WinRE) or your device’s manufacturer.
Warning: Do not delete or reformat these partitions, as this may prevent you from recovering Windows if needed.
Although you may safely ignore previously hidden partitions, you can hide them again by removing the partition’s assigned drive letter.
Select the Start button, type cmd, select and hold (or right-click) Command Prompt in the list of results, and then choose Run as administrator.
In the Administrator: Command Prompt window, type the following command, where driveLetter is the drive letter you want to remove:
mountvol driveLetter /d
For example, if the drive letter you want to remove is F, you would enter the following:
mountvol F: /d
After typing the command, press Enter.
The drive letter will no longer appear in File Explorer and Disk Management. You may close the command prompt window.