I'm using IIS 7.5 on Server 2008 R2 to run non-ASP sites, and they don't use .NET either.
Can ASP.NET be completely disabled/uninstalled, so that no ASP.NET security updates are required, and to fix minor annoyances like the appearance of aspnet_client
directories etc?
I think the asp.net features are installed with IIS. Have you tried disabling the mappings? You could probably also filter out aspx extensions.