If You are Installing PHP using FastCGI and Your WordPress gives you a 500 Error- Internal Server Error, Make sure that you have already established a server connection to mysql or mssql. Open I.E and then go to Tool–>Internet Options–>Click on Advanced Tab and then Un-check Show Friendly Error HTTP Messages. Click Apply. Now Refresh your page to see what is actually going on.

Also IIS does not support mod_rewrite so your permalink structure will look weired, here is the an example “/index.php/%year%/%monthnum%/%day%/%postname%/”. Inorder to have it such as the need for index.php is not required and it looks as if you were running it on Apache. Create a PHP file called permalinkhandler.php, save it in the root folder and include this code

 
<?php
$_SERVER['REQUEST_URI'] = substr($_SERVER['QUERY_STRING'], strpos($_SERVER['QUERY_STRING'], ':80')+3);
$_SERVER['PATH_INFO'] = $_SERVER['REQUEST_URI'];
include('index.php');
?>

Navigate to your site on the Server Manager on Windows and go to Error Pages, find Status Code 404 and point to that php file. Make sure you put it under the Execute URL on this site. Now go back to wordpress and chose the permalink structure you would like.