Windows 10 is showing an OEM Partition with a logical drive letter in Explorer [duplicate]

Solution 1:

This is a known issue with the April update of Windows 10. With this update, Windows sometimes erroneously assigns a drive letter to one of the normally hidden OEM or recovery partitions and subsequently complains about lack of free space on that partition. The solution is simply to remove that drive letter again.

Sometimes however this is not so easy since the standard Disk Management application refuses to touch the partition. The symptom being that the context menu for the partition in Disk Management shows nothing but "Help". In that case you'll have to run the diskpart command line tool from a command prompt with administrator privilege and then use the commands:

list volume
select volume <number of offending volume>
remove letter=<offending drive letter>
exit

to identify and remove the offending drive letter.