Classic ASP and ASP.NET 1.1

I have managed to get ASP.NET 1.1 up and running on my WS2008 R2 box. And I can debug within VS2003.

I however cannot get any classic asp pages to run and just says 500 internal server error. Creating a new simple asp page works. So clearly something wrong with the specific asp pages I am viewing. The asp pages are mixed with ASP.NET unfortunately.

How can I debug the asp pages and see what is going on?