Well, it looks to me like it's set up properly...and everything else seems to work fine. The page that errors out is http://admin/admin.php?add=4
Souhail, are you still here? As I mentioned, it looks to be pointing to the root just fine, but I'm still unable to add an administrator (or any other position on that screen) ?? What else can I check, or can I go in and "force" it in the database?