I think it has to be get_template_directory_uri()
instead of get_template_directory_url()
(lowercase i instead of lowercase l).
You also can use bloginfo
. See: http://codex.wordpress.org/Function_Reference/bloginfo
In your case:
<img src="<?php bloginfo('template_url'); ?>/images/logo.jpg" alt="<?php bloginfo('name'); ?>">
And of course make sure you're image is in the right location.