How to set a Disk to readonly on Windows?
For this you need to open a Admin Command Prompt and enter:

list volume
select volume (1)  Where the number is the number you saw on the list volume command
attribute volume set readonly

And to remove the readonly attribute, you simply type (select volume…clear readonly instead of set readonly)
list volume
select volume (1)  Where the number is the number you saw on the list volume command
attribute volume clear readonly