It may be hard to delete the articles. If you can, do so. If not, maybe just amend them so that they’re a bit more unique.
Think of your site content as a commodity. If you give it away to article sites for free, you’re undervaluing it. A well-placed ‘teaser’ article will bring traffic to your site – and that’s the ONLY reason it’s there!
In a nutshell: save the best content for your site and use articles to generate interest in it.
As to which directories, check out which ones appear at the top of the SERPs. In my experience, ezinearticles and articlesbase do well. Use isnare to distribute them, too.