This should work by putting the good IDs. The paged attribute is useless here as you’ll always show the same posts.
<div id="main_posts">
<?php
$temp = $wp_query;
$wp_query= null;
$wp_query = new WP_Query();
$wp_query->query(array(
'showposts' => 3,
//'paged' => $paged,
'post_type' => 'page',
'post__in' => array(1, 2, 3) // Your post IDs
));
?>
<?php //query_posts('showposts=3'); ?>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>
<div class="main_post">
<?php $image = get_post_meta($post->ID, 'Image', true); ?>
<a href="https://wordpress.stackexchange.com/questions/55037/<?php the_permalink(); ?>">
<img class="post_image" width="251" height="292" src="<?php echo $image; ?>" alt="" />
<div class="main_post_title"><a href="https://wordpress.stackexchange.com/questions/55037/<?php the_permalink(); ?>"><?php the_title(); ?></a></div>
</div>