Trying to remove thumbnail

Can anyone help, please?

Posts on the single post page contain both a small/thumbnail of the main image AND the main image.

I only want the thumbnail to appear on the front page and blog excerpt page, but not on the single page.

This code is from the single page. How can I tell it not to pick up the thumbnail image? Any ideas?

<!– Content –>
<div id=”content” class=”grid_9 <?php echo of_get_option(‘blog_sidebar’, ‘right’); ?>”>

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

// The following determines what the post format is and shows the correct file accordingly
$format = get_post_format();
get_template_part( ‘formats/content-‘.$format );
if($format == ”) {
get_template_part( ‘formats/content-standard’ );
}
wp_link_pages(‘before=<div class=”pagination”>&after=</div>’);

endwhile; ?>

<!– Comments –>
<?php comments_template(); ?>
<!– /Comments –>

<!– Comment links –>
<?php paginate_comments_links(); ?>
<!– /Comment links –>