How to Repair Windows 10 1803 “Hidden Drive” Bug

There’s a bug in the new Windows 10 1803 update that can mean you’re constantly plagued with rogue “Drive Full” notifications.  The problem occurs because a UEFI boot partition, which is hidden and used as part of Windows 10’s startup, security, and recovery system, has been assigned a drive Letter (e.g. D:) accidentally.

This isn’t so much of an issue in itself, except that the partition in question is pretty full and having it appear for the user, though they can’t do anything to damage it, means they will be regularly nagged with “Drive Full” notification pop-ups.

The drive letter for this partition cannot be removed in the Disk Management Console, and instead needs to be removed using the Command Line Diskpart disk partitioning tool.  This is an IT Pro-level tool and should be used with great care!  Doing the wrong thing with Diskpart can result in your PC becoming completely unbootable, resulting in having to completely reinstall Windows 10 and all your software and apps.

If you’re not very confident with IT, please do not attempt this fix yourself, instead ask a friend or colleague who is good with IT to do this for you.

You can quickly fix the problem though by following these instructions…

1. Open Command Prompt from the Start Menu
2. Type Diskpart and click through the UAC prompt
3. If you have more than one hard disk in your PC…

a. Type List disk and note the number of the disk on which Windows 10 is installed
b. Type Select Disk N where N is the number of the Windows installation disk

4. Type List Volume to see which partition has the offending drive letter. It will be a drive with a size measured in MB (Megabytes)
5. Type Select Volume N where N is the number of the UEFI partition that’s been given a drive letter, in my experience so far it’s the one called “Recovery
6. Type Remove Letter=N where N is the drive letter (maybe D or E) assigned to the UEFI partition
7. Type Exit to close Diskpart
8. Close the Command Prompt Window

Once this fix is implemented the problem will go away immediately, and it won’t bother you again.  I do stress though that using Diskpart is something you must always take great care with.

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