I found the problem with the 403 error. XAMPP modified my httpd-vhosts.conf file and I missed that one. Restoring the previous fixed that. Now I'm back to the original problem where
http://localhost/index.php only echoes back all my PHP commands but doesn't interpret/execute them.
Running
c:\php\php-cgi index.php returns my path followed by X-Powered By: PHP/5.2.10 Content-type: text/html <?php phpinfo(); ?>
but never displays the associated html file. So all indications are that PHP is running, just not interpreting commands properly.