Lynda.com subscriber Sarah Faraud uncovered an error at the 2:12 mark of the "Downloading and installing Drupal on a Mac" video in Drupal Essential Training. I stated:
Now the file itself was called settings.php and it's created by duplicating this default.settings.php. You can also just delete the word default and the period, but I prefer to leave a backup.
It turns out that deleting the original default.settings.php file causes problems, so just leave it there! My apologies to anyone who's been inconvenienced by this error.