Chris:

Actually, I've witnessed two apps running using Task Manager.  I added code
to my app to search for my open window and to bring that window to the front
and close the new app.  This is only successful in closing the new app.  My
existing window is not brought to the fore.  Here is the code I added to my
main method to control this issue:

string appname =
System.Reflection.Assembly.GetExecutingAssembly().GetName().Name;
splash.lMutex = CreateMutex(IntPtr.Zero, true, appname);
if( !lMutex.Equals(new System.IntPtr(0) ) )
{
   if(Marshal.GetLastWin32Error() == ERROR_ALREADY_EXISTS)
   {
       // need to find the splash window (not posting my actual window
classname or title
       IntPtr hFrmMain = FindWindow("{my_window_classname}",
"{my_window_title}");

       if(hFrmMain != IntPtr.Zero)
       {
           // bring that window to front
           SetForegroundWindow(hFrmMain);

           // exit this application
           return;
       }
       else
       {
           hFrmMain = IntPtr.Zero;
           // check to see if my other window is opened
           hFrmMain = FindWindow("{my_other_window_classname}",
"{my_other_window_title}");
           if(hFrmMain != IntPtr.Zero)
           {
               // bring that window to front
               SetForegroundWindow(hFrmMain);

               // exit this application
               return;
           }
       }
   }
}

// run the app (neither the splash window nor the other window are open)
Application.Run(new splash());

Do you see any logic errors?

Tim