I've searched everywhere but I don't seem to find a solution for this.
I have a WP installation that is using sub-domains and doesn't have yet any other sites besides the main site. What I want to do, without reinstalling from fresh, is enabling sub-directories.
I tried changing in the wp-config
define( 'SUBDOMAIN_INSTALL', true ); to
define( 'SUBDOMAIN_INSTALL', false ); and it allowed to create a site in a sub-directory but when viewing the site I can see only the HTML (no CSS) and I can't access the administration area of the site. I'm guessing there's something else that needs to be done so the paths work.