Hi,
I would be sure how you could get a 500 error calling a .asp page. It should be a 404 error, but you could use the ErrorDocument to let Joomla manage it. At this point, the Joomla routing could assign the URL to your default menu item, and if this is (let me say) an article you could get the com_content 500 error. With a different default menu you should get the 404 error. If this is the scenario you could redirect .asp pages, but I don't at the moment how to change a 500 to 404.

If my scenario is wrong, pls, add more information. If you prefer, send me a private message to info(at)selfget.com.

Kind regards,
Luigi

Yes,
this is a confirm that my hypothesis is right, just replace com_content with com_k2. The routing assign the call to com_k2, and this doesn't recognize the view, and issue a 500 error. You could intercept and redirect any .asp page, but no idea on how to change the 500 to 404 without changing the site menus. I hope this is muche clear now.

Kind regards,
Luigi