How to let ASPNET process run the Whidbey bits
This should be quite easy. After installing the right version of Whidbey, go to your framework directory, and run aspnet_regiis.exe under the whidbey directory.
>cd \WINDOWS\Microsoft.NET\Framework
>cd {The Whidbey installation version}
>aspnet_regiis -i
>iisreset
Your ASPNET process should be set to run whidbey correctly.