add comment box to category page

ok, it seems that the category pages are driven by archive.php. below is the archive.php code. i tried putting <?php comments_template(); ?> in different places throughout this page, but when i refresh, the comments box still does not appear.

please advise. thanks.

<?php get_header(); ?>
<?php get_sidebar(); ?>

<div id="content">
<?php if (have_posts()) : ?>
<?php $post = $posts[0]; ?>

<?php if (is_category()) { ?><h2><?php echo single_cat_title(); ?></h2>
<?php } elseif (is_day()) { ?><h2>Archive for <?php the_time('F jS, Y'); ?></h2>
<?php } elseif (is_month()) { ?><h2>Archive for <?php the_time('F, Y'); ?></h2>
<?php } elseif (is_year()) { ?><h2>Archive for the year <?php the_time('Y'); ?></h2>
<?php } elseif (is_tag()) { ?><h2>Tag: <?php single_tag_title(''); ?></h2>
<?php } elseif (is_search()) { ?><h2>Search results</h2>
<?php } elseif (isset($_GET['paged']) && !empty($_GET['paged'])) { ?><h2>Archives</h2>
<?php } ?>

<?php while (have_posts()) : the_post(); ?>
<h3><a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title(); ?>"><?php the_title(); ?></a></h3>
<div class="contenttext">
<?php the_content(''); ?>
</div>

<?php endwhile; ?>

<div class="navigation">
<p><span class="prevlink"><?php next_posts_link('&laquo; Previous entries') ?></span>
<span class="nextlink"><?php previous_posts_link('Next entries &raquo;') ?></span></p>
</div>

<?php else : ?>
<h2>Page not found!</h2>
<p>The page you trying to reach does not exist, or has been moved. Please use the menus or the search box to find what you are looking for.</p>
<?php endif; ?>

</div>
<?php get_footer(); ?>