I use the following (in my not yet visible site in development).
When I only want to show category 2:
$wp_query->set(‘cat’, ‘2’);
query_posts(”);
And then the loop starts:
if (have_posts()) : while (have_posts()) : the_post();
And so on. Note: this will display posts that are in cat 2, but also posts that are also in cat 2.