the Older iRite extension can be used with ASP Pages, however, it is compatible with DW 8 and CS3 only and cannot be installed along side HTML Editor.
we dont offer any extensions that will work with ASP pages any more.
You would need to find another Rich text editor extension that works with ASP.
HTML Editor is based on the CKEditor. CKEditor can be installed to ASP Sites. You could add the CKEditor package to your site manually, though this will take some coding experience: