Can't get blog to open

I have WinXP, Apahce, MySQL, PHP – all running and set up as localhost. I have installed the WP on localhost on my laptop. to try it out before I set the school’s blog site. I can log in as admin and get to the admin page to adjust dashboards etc. However, if I try to run the basic index.php page (which I assume is the site opening page), all I get is a directory listing. I have tried changing the dashboard, etc. This is the fifth time I have completely erased everything and started again with different blog titles. What on earth am I doing wrong? How do I get the blog to open for use???