The instance of Notification Services must be registered locally to use this method. The account used to drop the instance must have permission to drop databases. This includes membership in the dbcreator or sysadmin fixed server role.
When you delete an instance of Notification Services, you delete the database objects for the instance and its applications. If Notification Services created the databases, the databases are deleted. Otherwise, only the objects created by Notification Services in the instance and application schemas are deleted.
After you delete an instance, you should also unregister the instance, unless you are going to recreate the instance and want to use the same registry information.
Deleting the instance when some databases have open connections can leave the instance in an inconsistent state.
Make sure to stop the Notification Services engine components before deleting the instance.