RadToolBar for ASP.NET AJAX is the successor of RadToolBar for ASP.NET. The next generation of RadControls is built entirely on top of ASP.NET AJAX, utilizing its common client-side framework and programming model. RadControls for ASP.NET AJAX introduce a number of new features and performance optimizations, which are hard or impossible to implement in the regular ASP.NET suite. The integration and API models of the controls are also better, due to the common framework they share (RadControls for ASP.NET AJAX are shipped as a single assembly - Telerik.Web.UI.dll.) It is important to note that this new generation of RadControls will work only on ASP.NET 2.0 and 3.5 because of the underlying ASP.NET AJAX framework.
RadToolBar for ASP.NET AJAX has been completely re-written. Both the client and server-side APIs are brand new.
The following help article will be of help while migrating to the newer RadToolBar version:
Migrating from RadToolBar Classic to RadToolBar for ASP.NET AJAX
We hope this is helpful. If you need any assistance in the upgrade process or you have any other questions please contact us.