Most of the blogger started their blog on windows environment with IIS6 without any component installed for URL rewriting like ISAPI_REWRITE. And they don’t know the importance of URL rewriting but when they came to know about rewriting its too late. Following is the solution for those blogger who are willing to rewrite url on their blog.

< ?php
// This is the default file for the site. Usually index.php
$default = 'index.php';

// The name of this file.
// Set this value for the URL in Custom Error Properties of your website in IIS.
// Goto: IIS Manager > Websites > [Site Name] > Properties > Custom Errors >
// 404 & 404;2 & 404;3 > URL (Requires a '/' prefix in IIS).
$thisfile = '404-handler.php';

$_SERVER['ORIG_PATH_TRANSLATED'] = str_replace($thisfile, $default, $_SERVER['ORIG_PATH_TRANSLATED']);
$_SERVER['SCRIPT_FILENAME'] = str_replace($thisfile, $default, $_SERVER['SCRIPT_FILENAME']);
$_SERVER['ORIG_PATH_INFO'] = str_replace($thisfile, $default, $_SERVER['ORIG_PATH_INFO']);
$_SERVER['SCRIPT_NAME'] = str_replace($thisfile, $default, $_SERVER['SCRIPT_NAME']);
$_SERVER['PHP_SELF'] = str_replace($thisfile, $default, $_SERVER['PHP_SELF']);
$_SERVER['PATH_INFO'] = false;

$qs =&amp; $_SERVER['QUERY_STRING'];
$ru =&amp; $_SERVER['REQUEST_URI'];
$pos = strrpos($qs, '://');
$pos = strpos($qs, '/', $pos + 4);
$_SERVER['URL'] = $ru = substr($qs, $pos);
$qs = trim(stristr($ru, '?'), '?');

// Required for WordPress 2.8+
$_SERVER['HTTP_X_ORIGINAL_URL'] = $ru;

// Fix GET vars
foreach ( $_GET as $var =&gt; $val ) {
  if ( substr($var, 0, 3) == '404') {
    if ( strstr($var, '?') ) {
      $newvar = substr($var, strpos($var, '?') + 1);
      $_GET[$newvar] = $val;
    }
    unset($_GET[$var]);
  }
  break;
}
include($default);
?>

Follow the steps.

1. Create the file wp-404-handler.php in your base WordPress folder.
2. Set your sites 404 page to point to the wp-404-handler.php url. Most control panels at web hosts allow you to do this. If you’ve got the option to select between FILE and URL then choose URL.
3. Go to WordPress Options -> Permalinks in your WordPress admin page, and choose an appropriate structure for your links. I chose Custom with this pattern:/%year%/%monthnum%/%postname%.html
4. Enjoy Pretty URLs