Generally we do not guarantee responses to forum threads, although we make efforts to respond them, because they are a public resource. We guarantee, however, a 24hours response time for support tickets which require a subscription and 72hours response time for trial accounts. More information on the matter is available here - http://www.telerik.com/purchase/support-plans/devtools
As for the current question I have already replied to it in the support ticket that was opened by you, so I paste my answer below for the rest of the community.
The ASP.NET Development Server is the development server that comes with Visual Studio and is used for running your applications in a test environment. When Visual Studio is installed, it includes everything needed to start developing applications, for example .NET Framework and a development server. If there is something wrong with this setup, I would suggest reinstalling VS as there could be something corrupted in the current installation.
You can check the following article for more information about the different types of web servers that are used by Visual Studio: http://msdn.microsoft.com/en-us/library/58wxa9w5%28v=vs.100%29.aspx.
You can also try to open demos from IIS Express server in Visual Studio or host the demos to IIS server.
If you are still having difficulties after reviewing the information above, please provide a more detailed description of what you want to install, what you did before encountering the error and what do you want to achieve so that I can help you.
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