Thank you for writing.
Please, try to manually browse the Telerik assembly that contains RadRibbonBar. You could do this by following the steps below:
1. Right click on the Visual Studio toolbox and choose "Add Tab". Name the new tab "RadControls"
2. Right click on the new tab and navigate to "Choose items..."
3. Ensure in the Choose Toolbox Items form that you are in .NET Framework Components tab
4. Click the "Browse..." button and navigate to your install directory of RadRibbonBar. By default, it should be in "C:\Program Files\telerik\r.a.d.ribbonbar for WinForms Q4 2006\".
5. Choose RadRibonBar control and close the form
I hope this helps. Do not hesitate to contact me again if you have other questions.
the Telerik team