Displaying a category on a page

Here’s the orginal page template:

<?php get_header(); ?>

	<div id="content">

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

	<div class="post" id="post_<?php the_ID(); ?>">

	<span class="breadcrumbs"><a href="<?php echo get_option('home'); ?>/">Home</a> &raquo; <?php the_title(); ?></span>

	<h2 class="title"><?php the_title(); ?></h2>

		<div class="entry clearfloat">
		<?php the_content('<p class="serif">Read the rest of this page &raquo;</p>'); ?>

		<?php wp_link_pages(array('before' => '<p><strong>Pages:</strong> ', 'after' => '</p>', 'next_or_number' => 'number')); ?>

		</div>

	<?php edit_post_link('Edit this entry.', '<p>', '</p>'); ?>

	</div>

	<?php endwhile; endif; ?>

	</div>

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

How do I modify this template so that I can create a page template wherein it displays all the posts from a specific category..

I did this..didnt work though!

<?php
/*
Template Name: download
*/
?>

<?php get_header(); ?>

	<div id="content">

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

	<?php query_posts("cat=45")?>

	<div class="post" id="post_<?php the_ID(); ?>">

	<span class="breadcrumbs"><a href="<?php echo get_option('home'); ?>/">Home</a> &raquo; <?php the_title(); ?></span>

	<h2 class="title"><?php the_title(); ?></h2>

	</div>

	<?php endwhile; endif; ?>

	</div>

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

Thanks in advance for any help!