I don't know where the PagedList is, but I can answer your question about IIS 6.
The ".mvc" extension is required for IIS 6 because IIS 6.0 won't hand off an exception to ASP.NET unless the request is for an extension that is mapped to ASP.NET via the aspnet_isapi.dll.
So ASP.NET won't even know about these requests.
One workaround some have attempted is to map all requests to ASP.NET in IIS 6.0. We don't support this with MVC and it's generally not a good idea.
IIS 7.0 improves on IIS 6 because of its integrated pipeline.