Older/newer posts buttons on my .php site

I am trying to use wordpress to power my content feed on my website, without sending my viewers directly to the blog itself. In other words I am using snippets of wordpress code to fetch post data and display it on my php based site.

Please compare my current homepage
http://www.overtheedgecustoms.com
to its wordpress powered counterpart
http://www.overtheedgecustoms.com/wp.php

Blog is located here
http://www.overtheedgecustoms.com/blog/

I am trying to make the next necessary page of my website so it will display all posts in the blog. An archive if you will

please compare –
http://www.overtheedgecustoms.com/archive_all.php
to wordpress powered counterpart
http://www.overtheedgecustoms.com/wp-all.php

the problem I’m having is the oldes/newer posts buttons send the used to non existent pages thus landing them on a messed up version of my homepage. These same controls seem to work fine on the actual blog. I used the following code to power the buttons

<div class="navigation">
<div class="alignleft"><?php posts_nav_link('','','&laquo; Previous Entries') ?></div>
<div class="alignright"><?php posts_nav_link('','Next Entries &raquo;','') ?></div>
</div>

what have I done wrong, and how do I fix this? Also am I wasting my time trying to use wordpress to power my already built website, or should I just create a wordpress theme that would make it look like my site (please bear in mind I have never created a theme before).