diff -ur drupal-cvs/includes/bootstrap.inc drupal/includes/bootstrap.inc
--- drupal-cvs/includes/bootstrap.inc	2006-07-16 19:24:35.000000000 -0700
+++ drupal/includes/bootstrap.inc	2006-07-16 19:23:50.000000000 -0700
@@ -647,6 +647,12 @@
       // Initialize the default database.
       require_once './includes/database.inc';
       db_set_active();
+      $result = @db_query("SELECT name FROM {system} WHERE name = 'system'");
+      if($result && db_result($result) == 'system')
+      {
+        header("Location: install.php");
+        exit;
+      }
       break;
 
     case DRUPAL_BOOTSTRAP_SESSION: