The problem will be that you're running under IIS6 and if its on shared hosting you're unlikely to have sufficient control to make MVC run without "cheating" a bit.
Under IIS6 requests are only routed to the ASP.NET handlers (I don't promise to get the terminology right) if they have the right extension (.aspx, .asmx, .ashx, etc) with a nice MVC URL there's no extension at all so it doesn't get see by ASP.NET and hence the request won't hit the routing within your MVC app and so you get page not found.
Under IIS7 everything (ish) goes through the ASP.NET handler and so it just works.
So a couple of links to help, here's a stackoverflow question:
http://stackoverflow.com/questions/34194/asp-net-mvc-on-iis6
and here's Phil Haack on the subject:
http://haacked.com/archive/2008/11/26/asp.net-mvc-on-iis-6-walkthrough.aspx
Hope this helps.
http://haacked.com/archive/2008/11/26/asp.net-mvc-on-iis-6-walkthrough.aspx