Integrating AJAX into current site

I have seen many AJAX videos now that are good but they all start from a blank page.

I have sites I have built using ASP.NET 2 and I would like to implement ajax into those sites without rebuilding them.

Are there any videos/articles that show how to do this.

You don't have to rebuild a brand-new one. The point is to change Web.Config file. You can get template web.config file in C:\Program Files\Microsoft ASP.NET\ASP.NET 2.0 AJAX Extensions\v1.0.61025 (Beta 1 version) afterASP.NET AJAX v1.0 core Beta 1 release installed and then update web.config in your web application based on it. And you have to add some aspx source codes in your web pages, e.g. ScriptManager, UpdatePanel, etc.