As you have probably noticed, the version downloaded of our controls doesn't contain .Net 2.0 assemblies. The error that you receive is a bit self explanatory, the telerik controls need a higher version of the System.Web.Extensions assembly, than the one you are referencing, which is due to the fact that you are developing a .Net 2.0 project.
You could build 2.0 assemblies which could be used in your project, but the source code of our controls is not distributed with the trial version. You have to purchase them in order to get it.
the Telerik team
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