Removing a KMS host
This is purely a post to help people who have muliple KMS Host servers by accident!
To set a KMS Host back to being a KMS client:
First change the product key:
Right click on 'Computer', Select Properties and then 'change product key' at the bottom of the screen.
Find the applicable product key from here:
KMS Client Setup Keys
Thats the service disabled!
Ensure that you have also turned off the incoming/outgoing rules for KMS on the server (this doesn't happen by default).
Finally go to your DNS server and delete the entry for the KMS server, this can be found in Forward Lookup Zones\Your Domain\_tcp\_VLMCS - ensure that you are deleting the correct host!