Ok so it is working, I post it there in case that somebody has the same problem
using (TaskService ts = new TaskService())
{
// Create a new task definition and assign properties
TaskDefinition td = ts.NewTask();
td.RegistrationInfo.Description = "Does something";
//Setting to run as Local Service whether the user is logged in or not
td.Principal.LogonType = TaskLogonType.ServiceAccount;
td.Principal.UserId = "LocalService";
// Create a trigger that will fire the task at this time every other day
td.Triggers.Add(new DailyTrigger { DaysInterval = 2 });
// Create an action that will launch Notepad whenever the trigger fires
td.Actions.Add(new ExecAction("notepad.exe", "c:\\test.log", null));
// Register the task in the root folder
try { ts.RootFolder.RegisterTaskDefinition(@"Test", td, TaskCreation.CreateOrUpdate, "LocalService", null, TaskLogonType.ServiceAccount); }
catch (COMException ex) { Marshal.ThrowExceptionForHR(ex.ErrorCode); }
// Remove the task we just created
ts.RootFolder.DeleteTask(@"Test");
}