Disable Task Deletion
Computer Configuration\Administrative Templates\Windows Components\Task Scheduler
Prevents users from deleting tasks from the Scheduled Tasks folder.
This policy removes the Delete item from the Edit menu in the Scheduled Tasks folder and from the menu that appears when you right-click a task. Also, the system does not respond when users try to cut or drag a task from the Scheduled Tasks folder.
This policy appears in the Computer Configuration and User Configuration folders. If both policies are configured, the setting in Computer Configuration takes precedence over the setting in User Configuration.
This policy does not prevent administrators of a computer from using At.exe to delete tasks.