IIS 7 provides a much more module architecture than any previous version of IIS, leveraging this, Setup has been componentized in a way so that for security reasons only a static content web server is installed leaving the option for users to install any of the components they need. This helps for security (reduces surface attack) as well as for performance. The following link talks about the setup
http://learn.iis.net/page.aspx/130/understanding-setup-in-iis-7/
Anyway, you probably have to make sure that the ASP option under Application Development is installed and that the ASP ISAPI is allowed by going to the ISAPI and CGI Restrictions