displaying different number of posts on index and archive

i would like to display 4 posts on the index, and 10 on the archive. since i’m using a old version of WP none of the plug-ins for this seem to work.

i tried changing the options > reading > number of posts to 10 and putting this in the index:
<?php query_posts(‘showposts=4’); ?>
but this just shows the 4 latest posts even if i browse back to the older ones.

does any one know how i can change this line in my archive.php page to display 10 entries at a time?

<?php while (have_posts()) : the_post(); ?>

again, none of the plug-ins work for me ??
thanks a lot!