Using ISS and ASP can be difficult if you know what’s possible with Apache on *nix systems. Dynamic websites with request variables added to the url base are not that user and/or search engine friendly and need some serious remodeling.
On Apache you activate mod_rewrite and add a regex to modify the urls. But on Microsoft platforms, you’re left out in the cold.
So the ISAPI rewrite module from Helicon is good way to get the same functionality on MS platforms running ISS. You can modify and redirect the url, specify rules per site and in a global context, cloak websites (shouldn’t do it but possible), redirect based on HTTP values, and probably much more.
And, what is even more important. Their support is superb. Answers come quickly and are accurate. They even helped me right on the server to solve my problem. Not going to tell you what, but that’s not important. The fact is that support like that is hard to find.