There is a known issue with Noah's Classifieds where the application cannot detect that mod_rewrite is enabled on the server.

Fortunately, there is a simple fix for this. Open app/config.php and add this line before the final ?>:

$_SERVER["REWRITE_ON"]=1;

This line will tell the application that mod_rewrite is enabled and you will be able to use the Nice URL feature in Noah's Classifieds.