Show one category on index.php

I know there’s a plugin “ShowOneCategory” that seems to do what I want, but I can’t get it to work. I think I’ve followed the directions properly. This is the code (+ ‘post paged’ set):
<?php
/* Don't remove this line. */
/* index.php hacks */
//Set index.php to only show one category on main page
if ('/' == $_SERVER['REQUEST_URI'] || '/index.php' == $_SERVER['REQUEST_URI'])
$cat = 1;
/* --------------- */
require('./wp-blog-header.php');
?>
Is wrong?
Is there another way to show just a specified category on my front page? Please help me, I’m really desperate.
Thanks