/// <summary>
/// 更改Windows帐户密码
/// </summary>
/// <param name="username"></param>
/// <param name="oldPwd"></param>
/// <param name="newPwd"></param>
public static void ChangeWinUserPasswd(string username, string oldPwd, string newPwd)
{
  try
  {
    DirectoryEntry localMachine = new DirectoryEntry("WinNT://" + Environment.MachineName + ",computer");
    DirectoryEntry user = localMachine.Children.Find(username, "user");
    object[] password = new object[] { oldPwd, newPwd };
    object ret = user.Invoke("ChangePassword", password);
    user.CommitChanges();
    localMachine.Close();
    user.Close();
  }
  catch (Exception)
  {
    
  }
}

/// <summary>
/// 重置指定用户的密码
/// </summary>
/// <param name="userName">用户名</param>
/// <param name="password">新密码</param>
public static void ResetUserPassword(string userName, string password)
{
  string _Path = "WinNT://" + Environment.MachineName;
  DirectoryEntry machine = new DirectoryEntry(_Path);
  //获得计算机实例
  DirectoryEntry user = machine.Children.Find(userName, "User");
  //找得用户
  if (user != null)
  {
    user.Invoke("SetPassword", password); //用户密码
    user.CommitChanges();
  }
}