By far the easiest fix is to edit
wp-config.php to define two constants. (s)FTP into your site, or use a host supplied file manager, and add:
define( 'WP_SITEURL', 'http://www.abc.com/folder' );
define( 'WP_HOME', 'http://www.abc.com/folder' );
Those will be used instead of the information in the database. That will get your site up and running again. You won't be able to edit the URLs from the back-end so long as that is in place but the site should run just fine. I have even seen argument that you get a slight performance increase but have never tried to verify that claim.
Once the site is up, you can get into the database and fix the incorrect values if you'd like. There are instructions in the Codex that really boil down to:
- Open your database via PhpMyAdmin, or similar tool
- Navigate to the
- Edit the value for key 'siteurl'
- Edit the value for key 'home'