Index: modules/system/system.install
===================================================================
RCS file: /cvs/drupal/drupal/modules/system/system.install,v
retrieving revision 1.47
diff -u -p -r1.47 system.install
--- modules/system/system.install	28 Nov 2006 03:32:03 -0000	1.47
+++ modules/system/system.install	28 Nov 2006 13:48:10 -0000
@@ -694,7 +694,7 @@ function system_install() {
       db_query("CREATE INDEX {node_comment_statistics}_node_comment_timestamp_idx ON {node_comment_statistics} (last_comment_timestamp)");
 
       db_query("CREATE TABLE {files} (
-        fid int_unsigned NOT NULL default 0,
+        fid serial CHECK (nid >= 0),
         nid int_unsigned NOT NULL default 0,
         filename varchar(255) NOT NULL default '',
         filepath varchar(255) NOT NULL default '',