1) Backup your posts by using tools-->export
2) Download WP Suicide Plugin:
WordPress Suicide - Justinsomnia
3) Use the plugin. You can either completely wipe out your tables and start fresh, or just wipe out the content.
4(optional) Reinstall/Reconfigure Wordpress.
5) Upload your content via tools-->import-->Wordpress
That's it. No need for moving around files.