I think there is no need of IIS for running Openfire server. This uses Jetty sever. So u needn't to configure it in IIS. You can use it by running it and you can setup it by Web Admin interface which is running on http://127.0.0.1:9090.
You can use C# liberary(agsXMPP)for jabber protocol which can be used for communicating with openfire. You can find about this libarary here http://www.jabber.org/node/153
I just thought of sharing the method to use Openfire with IIS (in particular IIS7). With this, you will be able to use XMPP javascript libraries (e.g. Strophe, jwchat) with Openfire.
I am using **Openfire + IIS Express (webmatrix) + JWChat **to test web chatting and try to integrate JWChat to my ASP.NET project (developed by MS Visual Web Developer).
I have no idea how to do the reverse proxy configureation on webmatrix or ASP.NET running at my localhost.