how to make a page list one category.

This is what I would like to do:
I would like to create a page that shows posts only from one Category. I know there’s a plugin that can do this for the main page but the problem is that I don’t want the page to have the same layout as the main index.php. I guess I need to create a page called ‘Index2.php’ that lists only one category but I don’t now how to do this, any ideas?