New partitions may appear in File Explorer after installing the Windows 10 April 2018 Update (version 1803)

I have had exactly the same issue. An extra Drive appearing in my File Explorer and to date, no update to sort to thing out. Right Click it and click the property tag and look for the Security Tag, none there.... simple reason, I've got the Windows 10 Home Edition.

Anyway, today, I've tried to create a new file on another drive which only holds Adobe Lightroom Library details and I've got a message, identical to the brand new, unwanted Drive. States I do not have permission to enter the drive and says I've got to go and find the security Tag which is a non starter.

Why does Microsoft fiddle with things that clearly work.

Luckily, I've backed that drive up so I've reformatted the original and now I've got to copy the back up to the source, totally unnecessary.

Ill give the fix given here a go to get rid of the new drive, hopefully, this fix will help with the other issue as well!!

Microsoft is aware that previously-hidden partitions are improperly being assigned drive letters after installing the April 2018 Update.  As a result, they now appear in Disk Management and File Explorer.  These partitions are typically recovery partitions used by the Windows Recovery Environment or by the Original Equipment Manufacturer.  It is not recommended that you attempt to delete or reformat these partitions as this may have adverse effects on your ability to recover Windows.  Microsoft is currently working to address the issue in a future Windows Update, and we’ll update this thread when a solution becomes available. 

(Update 5/14/18: The solution that will soon be released via Windows Update will only prevent this issue from occurring for devices that install the April 2018 Update after the solution is released.  If you've already installed the April 2018 Update and are experiencing this issue, you'll need to follow the steps below if you want to hide these partitions.)

Although you can safely ignore these partitions, if you prefer do away with the low disk space warnings and hide the partitions so they no longer appear in File Explorer, you can do so by manually removing the partition’s assigned drive letter.  To do this:

1. Select the Start button, type cmd and then right-click Command Prompt in the search results and select Run as administrator.

2. In the Administrator:  Command Prompt window, type diskpart and press Enter.

3. Type list volume and press Enter.

4. Make note of the volume number for the drive letter you want to remove.  For example, if the drive letter you want to remove is Drive “G”, note the volume number for Drive G.

5. Type the following command, and press Enter. 

 select volume**<volume number>**

When typing this command, in place of <volume number>, substitute the volume number you made note of in Step 4.   In the example above, if the volume number for drive G is 5, you would type: select volume****5

6. Type the following command and press Enter.

remove letter= <drive letter>

When typing this command, in place of <drive letter>, substitute the drive letter you want to remove.  In this example, you would type: **remove letter=**G

7. Close the Command Prompt window.

After installing the April 2018 Update to upgrade to Windows 10 version 1803, a new partition appears in File Explorer.  I’m also constantly getting warnings that the partition is low in space, and there are no options to delete this partition.