I just realized that you’re talking about the browser “title” at the top; that wasn’t clear from your original post
Go into your header.php and at the top look for this line
<title><?php bloginfo('name'); ?> <?php if ( is_single() ) { ?> » Blog Archive <?php } ?> <?php wp_title(); ?> - <?php bloginfo('description'); ?> </title>
and remove
<?php if ( is_single() ) { ?> » Blog Archive <?php } ?>