I was just asking when or if xampp plans on adding ASP.NET SUPPORT
I don't think so. But you should be able to use e.g. mod_aspdotnet or mod_mono together with XAMPP/Apache.
(Maybe a XAMPP user want contribute to the project and provide a ASP.NET AddOn...)
and Ajax
That's beyond the scope of a webserver package like XAMPP.
It's the part of the webdeveloper (you) to write the server side code for Ajax requests handling. And of course the JavaScript code, which is executed in the users browser.
Well, most developer are using a "ready to use" Ajax framework, in a scripting language of their own choice (Perl,PHP,Ruby,...). We don't know, which one you want use.
(BTW: PEAR::HTML_AJAX is allready part of the XAMPP package)