How to delete unwanted block
Are you talking about the front page or a custom view?

If you are in the front page view, you have probably set the content type for slideshow images to be promoted to front page. Disable that in

admin/structure/types


by clicking manage and in the footer untick 'promoted to front page'

and they will stop showing up unformatted.
In that case you aren't actually talking about a 'block', but the system content that is displayed in the main content block defined in the themes page.tpl.php page with

&lt;!-- Page Content --&gt;
&lt;?php print render($page['content']); ?&gt;