IIRF is a freely available isapi filter that allows you to do rewriting similar to mod_rewrite on IIS.
You can find iconic rewrite here : http://iirf.codeplex.com/
The following example has been tested on IIRF 1.2 and redirects all requests without the www. subdomain to the same url including the www subdomain :
the '301' is the redirect code used by IIS
RewriteCond %{HTTP_HOST} ^joriso\.nl [I] RedirectRule ^/(.*) http://www.joriso.nl/$1 [R=301]