How Can I Make A Better CPU And I/O Perfomance?

[NewHotel]

i have text files, something like:
USER % THIS IS A USER LINE ALL CHAR EXCEPT '/n'
USERDATA % "DATA: ALL CHAR. it can be 3-20 lines."

so i need to read this file and make XML like that:
<?xml version="1.0" encoding="UTF-8"?>
<USERS>
<DATA>
<USER>THIS IS A USER LINE ALL CHAR EXCEPT '/n'</USER>
<USERDATA>DATA: ALL CHAR. it can be 3-20 lines.</USERDATA>
</DATA>
</USERS>

so i make it single thread. Here some code

public static void SingleThreadForEach(IEnumerable<string> LoadPath)
        {
            foreach (string itemFile in LoadPath)
            {
                string[] CurrentData = ReadText(itemFile);
                using (XmlWriter writer = XmlWriter.Create(itemFile.Replace(".txt", ".xml")))
                {
                    writer.WriteStartDocument();
                    writer.WriteStartElement("USERS");
                    writer.WriteStartElement("Data");
                    writer.WriteElementString("USER", CurrentData[0]); 
                    writer.WriteElementString("USERDATA", CurrentData[1]);
                    writer.WriteEndElement();
                    writer.WriteEndElement();
                    writer.WriteEndDocument();
                }
            }
        }


         public static string[] ReadText(string path)
        {
            string[] lines = File.ReadAllLines(path);
            string[] XMLData = new string[2];
            XMLData[0] = lines[0].Remove(0,9);
            XMLData[1] = string.Join(Environment.NewLine,lines.Where(s => s != lines[0]).ToArray()) ;
            return XMLData;
        }

So i need to make programm multithreaded. So i make it with Parallel.ForEach

public static void ParallelForEachReading(IEnumerable<string> LoadPath)
{
    Parallel.ForEach(LoadPath, itemFile =>
    {
        string[] CurrentData = ReadText(itemFile);
        using (XmlWriter writer = XmlWriter.Create(itemFile.Replace(".txt", ".xml")))
        {
            writer.WriteStartDocument();
            writer.WriteStartElement("USERS");
            writer.WriteStartElement("DATA");
            writer.WriteElementString("USER", CurrentData[0]);
            writer.WriteElementString("USERDATA", CurrentData[1]);
            writer.WriteEndElement();
            writer.WriteEndElement();
            writer.WriteEndDocument();
        }

    });
}

Here is my projectProject.rar