Edit Skype's config.xml

我正试图从代码编辑Skype的config.xml文件。它工作得很好，但在更改Skype后删除它并生成另一个，撤消我所有的更改。例如，代码:

public Core()
{
    try
    {
        var processes = Process.GetProcessesByName("Skype");
        if (processes.Length == 0)
        {
            AddRegistryKeys();
            RemovePlaceholder();
        }
        else
        {
            RestartSkypeAndRun(processes[0],
                () =>
                {
                    AddRegistryKeys();
                    RemovePlaceholder();
                });
        }
        Environment.Exit(0);
    }
    catch (Exception ex)
    {
        MessageBox.Show(string.Format("{0} - {1}", ex.GetType(), ex.Message), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
        Environment.Exit(-1);
    }
}
private static void RemovePlaceholder()
{
    string appDataPath = Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData);
    string skypePath = Path.Combine(appDataPath, "Skype");
    foreach (var configPath in Directory.EnumerateFiles(skypePath, "config.xml", SearchOption.AllDirectories))
    {
        string userConfig = File.ReadAllText(configPath);
        string fixedConfig = userConfig.Remove("<AdvertPlaceholder>1</AdvertPlaceholder>");
        File.Move(configPath, configPath + ".bak");
        File.WriteAllText(configPath, fixedConfig);
    }
}

private static void RestartSkypeAndRun(Process skypeProc, Action action)
{
    string skypeExePath = skypeProc.Modules[0].FileName;
    skypeProc.Kill();
    skypeProc.WaitForExit();
    Thread.Sleep(TimeSpan.FromMilliseconds(500)); //just in case
    action();
    Process.Start(skypeExePath);
}

那么怎么做呢?我不知道，除了阻止文件修改，例如改变ACL和文件的其他权限，设置只读属性等