Sorry for the caused inconvenience.
This usually happens when during the uninstall there are some files in use which could not be removed (If you have execute the Demos for Silverlight, the ASP.NET Development Server remains running and thus locks some file).
You could try to stop the Development Server and try again to uninstall the product from Add/Remove programs. Or you could also uninstall the product by using the msi file which you used for the installation. Just run the msi file again and choose the Remove option.
I hope this will help.
the Telerik team
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