I'm while using following code to display posts from merely a certain category flat in three rows. I've the horizontal display problem determined (using css) however with the next code it shows all posts and never posts from specific category.

<?php query_posts('showposts=5'); ?>
<?php query_posts('cat=7'); ?>
<?php $posts = get_posts('numberposts=5&offset=0'); foreach ($posts as $post) : start_wp(); ?>
<?php static $count1 = 0; if ($count1 == "5") { break; } else { ?>

<?php the_title(); ?>
<?php the_content(); ?>

<?php $count1++; } ?>
<?php endforeach; ?>

Any help could be greatly appreciated.

You are misunderstanding some concepts in query_posts and get_posts.

query_posts will be used within the loop. get_pages is not. If you wish to use query_posts, you don't have to produce the get_pages call. Use query_posts or get_pages to complete what you are attempting to do.

You have to mix your category parameters in query_posts.

<?php 
query_posts('showposts=5&cat=7');
//The Loop
if ( have_posts() ) : while ( have_posts() ) : the_post();
 ..
endwhile; else:
 ..
endif;

//Reset Query
wp_reset_query();
?>

If you wish to perform the same logic but with no Loop, just call

$posts = get_posts('numberposts=5&offset=0&category=7').

Browse the links I provided. They've information you must know how you can do the thing you need.