phpFox uses mod_rewrite to shorten URLs.
Old Method: http://www.yoursite.com/profile.php?user=natio
New Method (with mod_rewrite): http://www.yoursite.com/natio
Mod_rewrite is a module provided for use with Apache (HTTP Web Server). For those using IIS (Windows) there are a few alternatives to get this working...
Let me know if you have tested another filter that works with phpFox and I will add it to the list.