Index: wp-admin/includes/misc.php
===================================================================
--- wp-admin/includes/misc.php	(revision 11027)
+++ wp-admin/includes/misc.php	(working copy)
@@ -362,3 +362,220 @@
 		exit;
 	}
 }
+
+/**
+ * Updates the IIS web.config file with the current rules if it is writable.
+ * If the permalinks do not require rewrite rules then the rules are deleted from the web.config file.
+ * 
+ * 
+ * @return bool True if web.config was updated successfully
+ */
+function iis7_save_url_rewrite_rules(){
+	global $wp_rewrite;
+	
+	$home_path = get_home_path();
+	$web_config_file = $home_path.'web.config';
+
+	// Using is__writable() instead of is_writable() because of a bug in Windows PHP	
+	if ((!file_exists($web_config_file) && is__writable($home_path) && $wp_rewrite->using_mod_rewrite_permalinks()) || is__writable($web_config_file)) {
+		if ( iis7_supports_permalinks() ) {
+			$rule = $wp_rewrite -> iis7_url_rewrite_rules();
+			if ( !empty($rule) ) // 
+				return iis7_add_rewrite_rule($web_config_file, $rule);
+			else{
+				return iis7_delete_rewrite_rule($web_config_file);
+			}
+		}
+	}
+	return false;
+}
+// IIS 7 specific functions
+
+/**
+ * Check if IIS 7 supports pretty permalinks
+ * 
+ * 
+ * @return bool
+ */
+function iis7_supports_permalinks(){
+	// First we check if the DOMDocument class exists. If it does not exist,
+	// which is the case for PHP 4.X, then we cannot easily update the xml configuration file,
+	// hence we just bail out and tell user that pretty permalinks cannot be used.
+	// This is not a big issue because PHP 4.X is going to be depricated and for IIS it
+	// is recommended to use PHP 5.X NTS.
+	$supports_permalinks = class_exists('DOMDocument') && iis7_url_rewrite_loaded();
+	return apply_filters('iis7_supports_permalinks', $supports_permalinks);
+}
+
+/**
+ * Check if rewrite rule for WordPress already exists in the IIS 7 configuration file
+ * 
+ * 
+ * @return bool
+ * @param string $filename The file path to the configuration file
+ */
+function iis7_rewrite_rule_exists($filename)
+{	
+	if (!file_exists($filename)) return false;	
+	if (!class_exists('DOMDocument')) return false;
+	
+	$doc = new DOMDocument();
+	if ($doc -> load($filename) === false) return false;
+	$xpath = new DOMXPath($doc);
+	$rules = $xpath -> query('/configuration/system.webServer/rewrite/rules/rule[@name=\'wordpress\']');
+	if ($rules -> length == 0) 
+		return false;
+	else
+		return true;	
+}
+
+/**
+ * Delete WordPress rewrite rule from web.config file if it exists there
+ * @return 
+ * @param string $filename Name of the configuration file
+ */
+function iis7_delete_rewrite_rule($filename)
+{	
+	// If configuration file does not exist then rules also do not exist so there is nothing to delete
+	if (!file_exists($filename)) return true;
+	
+	if (!class_exists('DOMDocument')) return false;
+	
+	$doc = new DOMDocument();
+	$doc -> preserveWhiteSpace = false;
+
+	if ($doc -> load($filename) === false) return false;
+	$xpath = new DOMXPath($doc);
+	$rules = $xpath -> query('/configuration/system.webServer/rewrite/rules/rule[@name=\'wordpress\']');
+	if ($rules -> length > 0) {
+		$child = $rules -> item(0);
+		$parent = $child -> parentNode;
+		$parent -> removeChild($child);
+		$doc -> formatOutput = true;
+		saveDomDocument($doc, $filename);
+	}
+	return true;
+}
+
+/**
+ * Add WordPress rewrite rule to the IIS 7 configuration file.
+ * 
+ * 
+ * @return bool
+ * @param string $filename The file path to the configuration file
+ * @param string $rewrite_rule The XML fragment with URL Rewrite rule
+ */
+function iis7_add_rewrite_rule($filename, $rewrite_rule)
+{	
+	if (!class_exists('DOMDocument')) return false;
+	
+	// If configuration file does not exist then we create one.
+	if (!file_exists($filename)) {
+		$fp = fopen( $filename, 'w');
+		fwrite($fp, '<configuration/>');
+		fclose($fp);
+	}
+	
+	$doc = new DOMDocument();
+	$doc -> preserveWhiteSpace = false;
+
+	if ($doc -> load($filename) === false) return false;
+	
+	$xpath = new DOMXPath($doc);
+
+	// First check if the rule already exists as in that case there is no need to re-add it
+	$wordpress_rules = $xpath -> query('/configuration/system.webServer/rewrite/rules/rule[@name=\'wordpress\']');
+	if ($wordpress_rules -> length > 0) return true;
+
+	// Check the XPath to the rewrite rule and create XML nodes if they do not exist
+	$xmlnodes = $xpath -> query('/configuration/system.webServer/rewrite/rules');
+	if ($xmlnodes -> length > 0){
+		$rules_node = $xmlnodes -> item(0);
+	}
+	else{
+		$rules_node = $doc -> createElement('rules');
+		
+		$xmlnodes = $xpath -> query('/configuration/system.webServer/rewrite');
+		if ($xmlnodes -> length > 0){
+			$rewrite_node = $xmlnodes -> item(0);
+			$rewrite_node -> appendChild($rules_node);
+		}
+		else{
+			$rewrite_node = $doc -> createElement('rewrite');
+			$rewrite_node -> appendChild($rules_node);
+
+			$xmlnodes = $xpath -> query('/configuration/system.webServer');
+			if ($xmlnodes -> length > 0){
+				$system_webServer_node = $xmlnodes -> item(0);
+				$system_webServer_node -> appendChild($rewrite_node);
+			}
+			else{
+				$system_webServer_node = $doc -> createElement('system.webServer');
+				$system_webServer_node -> appendChild($rewrite_node);
+		
+				$xmlnodes = $xpath -> query('/configuration');
+				if ($xmlnodes -> length > 0){
+					$config_node = $xmlnodes -> item(0);
+					$config_node -> appendChild($system_webServer_node);
+				}
+				else{
+					$config_node = $doc -> createElement('configuration');
+					$doc -> appendChild($config_node);
+					$config_node -> appendChild($system_webServer_node);
+				} 
+			}		
+		}
+	}
+	
+	$rule_fragment = $doc -> createDocumentFragment();
+	$rule_fragment -> appendXML($rewrite_rule);
+	$rules_node -> appendChild($rule_fragment);
+
+	$doc -> formatOutput = true;	
+	saveDomDocument($doc, $filename);
+
+	return true;	
+}
+
+/**
+ * Saves the XML document into a file
+ * 
+ * @param DOMDocument $doc
+ * @param string $filename
+ */
+function saveDomDocument($doc, $filename)
+{
+	$config = $doc -> saveXML();	
+	$config = preg_replace("/([^\r])\n/", "$1\r\n", $config);
+	$fp = fopen($filename, 'w');
+	fwrite($fp, $config);
+	fclose($fp);
+}
+
+/**
+ * Workaround for Windows bug in is_writable() function
+ * 
+ * @return 
+ * @param object $path
+ */
+function is__writable($path) {
+//will work in despite of Windows ACLs bug
+//NOTE: use a trailing slash for folders!!!
+//see http://bugs.php.net/bug.php?id=27609
+//see http://bugs.php.net/bug.php?id=30931
+
+    if ($path{strlen($path)-1}=='/') // recursively return a temporary file path
+        return is__writable($path.uniqid(mt_rand()).'.tmp');
+    else if (is_dir($path))
+        return is__writable($path.'/'.uniqid(mt_rand()).'.tmp');
+    // check tmp file for read/write capabilities
+    $rm = file_exists($path);
+    $f = @fopen($path, 'a');
+    if ($f===false)
+        return false;
+    fclose($f);
+    if (!$rm)
+        unlink($path);
+    return true;
+}
+?>
\ No newline at end of file