IIS7 and ASP.NET
IIS7 provides two modes while integrating with ASP.NET. One is classic mode as back-compatibility approach, in which ASP.NET plays a role as an ISAPI extension (aspnet_isapi.dll) -- standalone app domain. Another is integrated mode -- "enabling ASP.NET components to become full members of the IIS request processing pipeline", in which aspx, web forms and ASP.NET modules are working side by side with native C++ IIS modules in the same pipeline. That means they can take advantage of each other's different services.
Reference:
Explore The Web Server For Windows Vista And Beyond
Nice figure inside the article above
