Close, but you mixed the quick model (using AddTask) with the full control model (which uses TaskDefinition and RegisterTaskDefinition). Your corrected code would be:
TaskDefinition td = TaskService.Instance.NewTask(); // Setup and add trigger DailyTrigger dt = new DailyTrigger(); dt.StartBoundary = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, startHour.Hours, startHour.Minutes, startHour.Seconds); td.Triggers.Add(dt); // Setup and add action td.Actions.Add(execPath); // Add settings td.Settings.StartWhenAvailable = true; td.Settings.Compatibility = TaskCompatibility.V2_3; td.Settings.RestartInterval = TimeSpan.Zero; // Register definition TaskService.Instance.RootFolder.RegisterTaskDefinition("Task", td);