Figuring out how to configure the multi-site feature in Drupal can be daunting. There is a lot of conflicting material on the net, perhaps due to the long life of drupal and different incarnations. The most recent documentation on the Drupal support site talks about editing the httpd.conf (Apache Hosts) file to handle multiple domains in Drupal. Unfortunately, most hosting companies don't let you access the httpd.conf file. Some charge for it, and some will make changes for you if you submit a support ticket. Laborious!

Fortunately it isn't nearly that complicated.