Guest access not working in moodle

I'm new to using moodle. I have downloaded Moodle 2.9 version. I'm doing the integration of drupal and moodle. to just showing the moodle courses in drupal side. I have created 10 courses in moodle among these 5 courses can be taken by guest user. To test these functionalities I clicked the button "Login as a Guest User" in moodle login page. But it shows "Invalid user, try again". After long searching I found that, there is no guest user record in "mdl_user" table of moodle database. Now what can I do??? Can I insert guest user details manually?????? Thank you.