Chose subdomain setup, but somehow have sub-directory setup

Just upgraded my WP 2.9 to WP 3.0 and went to Multisite to add new functionality. I intended to use subdomains and chose that, but somehow I have a sub-directory setup. I have not created any test blogs on it yet, but wondering if I could start over with the wp-config file and re-run the setup over again, or am I stuck?