Is it possible that you have some rules configured in IIS using modules like the UrlRewriter IIS module?
Is it possible the web server is behind a proxy server?
Are you running any custom features on your site?
Are you using SSL?
Is there a specific reason you did not install it in a root level and instead installed it in a sub flder named ITSForums? Your root level url currenlty has no page being served.
I cannot reproduce the problem when running installed in a sub folder. I suspect some kind of web configuration issue on your server but I have no way of knowing without looking around in IIS settings.