System.Timers.Timer "single-threaded" usage

I`d like some job be periodically done. This job might be writing files, some processing with resourse handling + sometimes it might be time-consuming. A good candidate for periodic tasks is a Timer clas from System.Timers namespace. However, it raises Elapsed event each time in different thread.

Now imagine I have 500ms Timer period, and the thread from previous Elapsed event did not finished, so the resourses were not released. A thread from "current" Elapsed event tries to get theses resourses, and we`ve got a conflict. I see a solition like the following:

class FolderMonitor
{
 Timer monitoringTimer = new Timer(500);

 public FolderMonitor(string folderName)
 {
   monitoringTimer.Elapsed += new ElapsedEventHandler(monitoringTimer_Elapsed);
   monitoringTimer.Start();
 }

  void monitoringTimer_Elapsed(object sender, ElapsedEventArgs e)
        {
            monitoringTimer.Enabled = false;
            try
            {
                //a work with resourses, for example, 
                //take the files from folder and convert them into other format
            }
            finally
            {
                monitoringTimer.Enabled = true;
            }

        } 
}

Is it OK?
Shall it work s I expect, i.e. no other thread can now even access resourses, while one is working?
Any disadvantages of such solution?

Tags: C#, Time