CiviCRM settings file does not exist
I'm a little confused here - you say that the Modules overlay confirms it's installed, but any attempt to enable it produces the error. You shouldn't have to enable it anywhere - you run the install page and then it is installed and automatically enabled in Drupal.

So on the modules page is it just listed there, or is it checked to show that it is actually turned on?

I want to make sure where we stand on that before looking at other causes.