Windows 10’s April 2018 Update (version 1803) brought various new features and removed some others, but also introduced a bug to many systems that caused an extra drive to be listed under “This PC.” Most annoying of all, the bug causes Windows to display an error prompt about the drive being nearly full.
“Low Disk Space. You are running out of disk space on Local Disk (E:). Click here to see if you can free space on this drive.”