http://127.0.0.1/mutillidae 404 error

I'm reading from a book. I have windows 7 VBox with guest additions installed. I installed xampp and started Apache and MySQL. I downloaded Mutillidae. I extracted the folder from the zip. Copied it to C:\XAMPP\htdocs, then I opened up internet explorer and typed http://127.0.0.1/mutillidae. I get this


Warning: require_once(./includes/constants.php): failed to open stream: No such file or directory in C:\xampp\htdocs\mutillidae\index.php on line 6
Fatal error: require_once(): Failed opening required './includes/constants.php' (include_path='C:\xampp\php\PEAR') in C:\xampp\htdocs\mutillidae\index.php on line 6