Need help with WP...

I need help with wp site...
on site pc-informer.com , I want to show thumbnail pic on homepage and full size picture on post page.
My question is how to remove bigg picture from hompage and leave only thumbnail like in 3rd post?
Code for homepage is:

<?php get_header(); ?>
        <div class="span-24" id="contentwrap">
            <div class="span-13">
                <div id="content">   
                <?php if(is_home()) { include (TEMPLATEPATH . '/featured.php'); } ?>       
                    <?php if (have_posts()) : ?>   
                        <?php while (have_posts()) : the_post(); ?>
                        <div class="postwrap">
                        <div <?php post_class() ?> id="post-<?php the_ID(); ?>">
                            <h2 class="title"><a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>"><?php the_title(); ?></a></h2>
                            <div class="postdate">Posted by <strong><?php the_author() ?></strong> on  <?php the_time('F jS, Y') ?> <?php if (current_user_can('edit_post', $post->ID)) { ?> | <?php edit_post_link('Edit', '', ''); } ?></div>
                            <div class="entry">
                                <?php if ( function_exists('has_post_thumbnail') && has_post_thumbnail() ) { the_post_thumbnail(array(200,160), array('class' => 'alignleft post_thumbnail')); } ?>
                                <?php the_content(''); ?>
                                <div class="readmorecontent">
                                    <a class="readmore" href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title_attribute(); ?>">Read More &raquo;</a>
                                </div>
                            </div>
                           
                        </div><!--/post-<?php the_ID(); ?>-->
                        </div>
                <?php endwhile; ?>
                <div class="navigation">
                    <?php if(function_exists('wp_pagenavi')) { wp_pagenavi(); } else { ?>
                    <div class="alignleft"><?php next_posts_link('&laquo; Older Entries') ?></div>
                    <div class="alignright"><?php previous_posts_link('Newer Entries &raquo;') ?></div>
                    <?php } ?>
                </div>
                <?php else : ?>
                    <h2 class="center">Not Found</h2>
                    <p class="center">Sorry, but you are looking for something that isn't here.</p>
                    <?php get_search_form(); ?>
           
                <?php endif; ?>
                </div>
            </div>
       
        <?php get_sidebars(); ?>
    </div>
<?php get_footer(); ?>

Code (markup):

 

Just replace line #14 with this:
<?php echo strip_tags(get_the_content(), '<p><a><b><br><li><ul>'); ?>

 

Some themes have use-thumbnail option for the post at home page. Did you try checking into that?

 

I would check your theme options.