Here's my situation - I've had an ASP.NET application running in production for a long time now (Framework 2.0) and recently migrated from one root directory to another by switching the app's home path in IIS. Everything is running just fine, except any classic .asp scripts. When you hit them with a browser, they start to download like a standard text file.
The application config has not been changed, just the root home directory. Also, I have other applications on the same machine that do allow .asp to execute within them.
Before answering, keep in mind: 1 - this was all working in my ASP.NET app before I changed the home directory 2 - classic ASP is enabled 3 - classic ASP pages run from other virtual directories, so the extension mapping seems fine