Ajax.net-if you want to add the Ajax function to some places in the application, use ajax.net.

Ajax.net: http://www.codeplex.com/Release/ProjectReleases.aspx? Projectname = ajaxpro
Ajax.net professional provides ajaxpro. dll and ajaxpro.2.dll for 03 and 05.
Supports lightweight frameworks.
If you only want to add the Ajax function to some places in the application, use ajax.net. It is easier to use than Rico, and the tool is easy to use.
If it is full-site Ajax, you still need to use the Atlas of Ms. The drag operation should also support well. I believe it can save a lot of development time.

Reinstall 03 on weekends and install 2005.
Study C #2.0