Index: update-core.php
===================================================================
--- update-core.php	(revision 12549)
+++ update-core.php	(working copy)
@@ -219,14 +219,24 @@
 
 	@set_time_limit( 300 );
 
+	$versions_file = $wp_filesystem->wp_content_dir() . 'upgrade/version-current.php';
+	if ( !$wp_filesystem->copy($from . '/wordpress/wp-includes/version.php', $versions_file) ) {
+		$wp_filesystem->delete($from, true);
+		return new WP_Error( 'copy_failed', __('Could not copy files.') );
+	}
+
+	$wp_filesystem->chmod($versions_file, FS_CHMOD_FILE);
+	require_once( WP_CONTENT_DIR . '/upgrade/version-current.php' );
+	$wp_filesystem->delete($versions_file);
+
 	$php_version    = phpversion();
 	$mysql_version  = $wpdb->db_version();
-	$required_php_version = '4.3';
-	$required_mysql_version = '4.1.2';
-	$wp_version = '2.9';
 	$php_compat     = version_compare( $php_version, $required_php_version, '>=' );
 	$mysql_compat   = version_compare( $mysql_version, $required_mysql_version, '>=' ) || file_exists( WP_CONTENT_DIR . '/db.php' );
 
+	if ( !$mysql_compat || !$php_compat )
+		$wp_filesystem->delete($from, true);
+
 	if ( !$mysql_compat && !$php_compat )
 		return new WP_Error( 'php_mysql_not_compatible', sprintf( __('The update cannot be installed because WordPress %1$s requires PHP version %2$s or higher and MySQL version %3$s or higher. You are running PHP version %4$s and MySQL version %5$s.'), $wp_version, $required_php_version, $required_mysql_version, $php_version, $mysql_version ) );
 	elseif ( !$php_compat )