Contributed By: Wally Mead [MS]
You can't undo Network Discovery. What you do is either disable the discovery method, or just not schedule it to run. It runs on the schedule configured.

Contributed By: Martin Santospirito (MS)
If the tab is greyed out, you don't have the permission to change it. Login with the user the service uses, this one has the full rights and give yourself the right to change it.