Trouble with XML

Hi

I'm having trouble with some serialization to XML.

I'm trying to a serializable class to an xml file but it gets appended with a whole new xml root and contents everytime and also isn't working well when i try to read from it. Here's code and the XML file, can someone fix this? Thanks

private void ManageFiles(string destDirectory, string imageFileName)
        {
            try
            {
                InitializeFile();
                SimulatorConfig objSimulatorConfig = new SimulatorConfig();
                objSimulatorConfig.lstFileManage = new List<string>();
               
                System.IO.FileStream fs = new FileStream(System.IO.Directory.GetCurrentDirectory() + "\\ManagerFile.xml", FileMode.OpenOrCreate);
                XmlSerializer serializer = new XmlSerializer(typeof(SimulatorConfig));
               
                //Check for 51 file limit
                XmlReader rdr = XmlReader.Create(fs);
               
                objSimulatorConfig = (SimulatorConfig)serializer.Deserialize(rdr);

                if (objSimulatorConfig.lstFileManage.Count() > objSimulatorConfig.iMaxFiles)
                {
                    for (int i = objSimulatorConfig.iMaxFiles - 4; i <= objSimulatorConfig.iMaxFiles - 1; i++)
                    {
                        System.IO.File.Delete(objSimulatorConfig.lstFileManage.ElementAt(i).ToString());
                    }
                }

                objSimulatorConfig.lstFileManage.Add(destDirectory + "\\" + imageFileName); ;
                serializer.Serialize(fs, objSimulatorConfig);
                fs.Close();
            }
            catch (Exception ex)
            {
                ex = new Exception("",ex.InnerException);
                throw ex;
            }
        }

INCORRECT HANDLING OF NODE
----------------------------------------------------

<?xml version="1.0"?>
<SimulatorConfig xmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <iMaxFiles>51</iMaxFiles>
  <lstFileManage>
    <string>C:\Image\C6_0_0.tif</string>
    <string>C:\Image\C6_0_1.tif</string>
    <string>C:\Image\C6_0_2.tif</string>
</SimulatorConfig><?xml version="1.0"?>
<SimulatorConfig xmlns:xsd="http://www.w3.org/2001/XMLSchema"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <iMaxFiles>51</iMaxFiles>
  <lstFileManage>
    <string>C:\Image\C7_0_0.tif</string>
  </lstFileManage>
</SimulatorConfig>
ManagerFile.xml