The following procedures are only a temporary solution to solve the Single Sign On challenge for Moodle and Drupal. It is not a proper way to solve the problems, I am sure it is not secure in anyway. I will stop using this method once the proper way was found. You had been warned.
Drupal and Moodle are on the same domain mydomain.com and they can be accessed
from http://www.mydomain.com and http://www.mydomain.com/moodle.