Custom category loop issues

I don’t see any previous_posts_link() and next_posts_link() constucts so look at the WordPress Default themes index.php for examples of those.

But you might try changing that last query from:

<?php query_posts('category_name=windows7-guides'.'&paged=' . $paged); ?>

to

<?php
$paged = (get_query_var('paged')) ? get_query_var('paged') : 1;
query_posts('category_name=windows7-guides'.'&paged=' . $paged);
?>

Seems you have plugins handling the navigation, and you’ve got includes in your loop, so maybe need to point you here:

http://www.google.com/search?q=wordpress+pagination+and+query

A good wealth of these would still be relevant.
http://wordpress.org/tags/pagination
http://wordpress.org/tags/paged

The key here, as Michael has already shown in his initial response, is setting up the $paged variable, or at least the paged parameter inside the query_posts line, since this ultimately controls, and sets, the offset positions in the query, ie. your LIMIT clause in the end SQL query..

Ideally what i believe you should do, is drop the built-in paging and write your own. I say this simply because i don’t think query_posts is equipped to deal with 4 queries (all using query_posts) and paging them..

You could look at plugins for examples, but i can’t say i know any particular plugins specifically that cover this (i’m sure it’s been done though).