use permalink custom strucutre in wordpress windows iis7
if you want to use custom strucutre = /%postname%/ then yo need to use below code in .htaccess if linux or in URL rewrite if windows 2008
<IfModule mod_rewrite.c> RewriteEngine On RewriteBase / RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule . /index.php [L] </IfModule> Reference
http://wordpress.org/support/topic/page-not-found-after-changing-permalink-to-postname