I’m in the process of pointing a domain root to a Wordpress install that resides in a /wordpress folder below the root. I’m following these instructions—or rather trying to!
I first modified the Site address (URL) from https://store.mydomain.com to https://store/mydomain.com/wordpress, moved (instead of copying) the /wordpress/.htaccess and index.php files to the root, cleaned up those files how they should have been in the first place (!), and then promptly lost access to wp-admin.
I backed up the site content before starting all of this but, naturally, elected not to back up the Wordpress database. Which was a bit silly.
Fortunately, I was able to roll back to the start—without access to wp-admin, by modifying the value of the siteurl row in the wp_options table (in the MySQL database via phpMyAdmin).
This article also has some great options to get you up and running again without modifying the database: http://codex.wordpress.org/Changing_The_Site_URL