Random Posts on Main Page Messing Up

O.k, I placed the code

<?php if (have_posts()) : ?>
<?php

query_posts('orderby=rand');

global $more;
// set $more to 0 in order to only get the first part of the post
$more = 0;
?>

before <?php while (have_posts()) : the_post(); ?>

on the main page, which works, but now when I click on categories or archive links, it just keeps giving me random posts. Any work around this?

Thanks!