I was recently setting up a Drupal install on IIS7. The setup instructions required that the IIS_IUSRS account be given, temporarily, write access to the settings.php file so it could write the database configuration to the file.
In the end I had to edit the file myself and input the database configuration details myself. What I am wondering is why the instruction specified the IIS_IUSRS account rather than the IUSR account.
Perhaps I am not properly understanding how IIS_IUSRS and IUSR differ.