Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.229
diff -u -p -r1.229 system.install
--- modules/system/system.install	10 Jan 2008 22:47:17 -0000	1.229
+++ modules/system/system.install	11 Jan 2008 00:48:25 -0000
@@ -183,7 +183,14 @@ function system_requirements($phase) {
     );
   }
 
-  // Test files directory
+  // Before installation, check if default.settings.php exists.
+  $default_settings = './sites/default/default.settings.php';
+  if ($phase == 'install' && !file_exists($default_settings)) {
+    // TODO: The error message should be made more helpful. See issue #208662.
+    drupal_set_message(st('%name has been deleted.', array('%name' => $default_settings)), 'error');
+  }
+
+  // Test files directory.
   $directory = file_directory_path();
 
   // For installer, create the directory if possible.