writing to xml

I have a text file and an xml file in c:\mcad which is open to everyone. I can write to the text file with the code below but get access denied to the xml.


public void Page_Load(object sender, System.EventArgs e)
		{
			StreamWriter sw = new StreamWriter(@"c:/mcad/audit.txt");
				
			sw.WriteLine("\n"+"col3"+"\t"+"col4");
			sw.Close();

			//write to xml
			XmlTextWriter xr = new XmlTextWriter(@"c:/mcad/XMLFile1.xml",null);
			xr.WriteStartDocument();
			xr.WriteStartElement("Product");
			xr.WriteElementString("Name","Jack");
			xr.WriteElementString("Address","Jack");
			xr.WriteElementString("Address2","Jack");
			xr.WriteElementString("Email","Jack");
			xr.WriteEndElement();
			xr.Flush();
			xr.Close();
		}

Any help appreciated. Thanks