Thank you for contacting the Telerik Support Team.
The Live Demos are configured only to look for the SQL instance called "SQLEXPRESS". We are aware of that issue, however, currently I cannot provide any estimate when it will be fixed.
In order to handle that you must change the DB connections strings in the Live Demos' web.config file, so that they refer to the name of your SQL instance.
If you need further assistance on this regard, do let us know.