changing the structure of an install

Hi,

I have installed wordpress onto our server.
I want a custom php to pull in the blog posts. I have researched this and it seems you can do this using the Loop.
If my php file is called index.php then this seems to work ok but as soon as i rename the file or move to the parent folder it stops working and cannot find the posts.

I make it wordpress ready using
require(‘wp-blog-header.php’);
but as soon as i rename the index.php file it stops working.

I ideally with to pull in the blogs to my existing website that resides in the parent folder.

Any help would be massively appreciated as Ive been looking for a solution all day now – and im still scratching my head..

Thanks
Tim