// Better version of
    http://pastebin.com/ut1Sh2sF
     
    <?php
    include ("./inc/template/header-index.php");
    if(isset($_SESSION['username']))
    {
            header("Location: cpu.php");
    }
      $d =(isset($_GET['do']) && $_GET['do'] == 'check');
    {
     if(isset($_POST['username']) && isset($_POST['password']))
     {
     $uName = mysql_real_escape_string($_POST['username']);
     $pWord = mysql_real_escape_string(md5($_POST['password']));   
     $aSQL = mysql_query("SELECT * FROM users WHERE username = '".$username."' AND password = '".$password."'") or die(mysql_error());
    if(!mysql_num_rows($aSQL))
     {
     $error = "Enter you username and password to log in";
    }else{
      $_SESSION['username'] = true;
      $_SESSION['password'] = $password;
            header("Location: cpu.php");
     }
    }
    ?>
     <?php if(isset($error)) { echo "".$error.""; } ?>
    <form action="/index.php?do=check" method="post">
            <input type="text" name="username" placeholder="Username" /><br>
            <input type="password" name="password" placeholder="Password" /><br>
            <input type="submit" name="login" value="Login" />
    </form>