Assembly missing error in Windows Phone 7

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C#

Visual-Studio

Hi experts. I have download some sample windows phone 7 projects. When i have to try to execute the project it show error. That error is

Error	1	Unable to load the metadata for assembly 'WindowsPhoneWatermarkTextBoxControl'. This assembly may have been downloaded from the web.  See http://go.microsoft.com/fwlink/?LinkId=179545.  The following error was encountered during load: Could not load file or assembly 'WindowsPhoneWatermarkTextBoxControl, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null' or one of its dependencies. Operation is not supported. (Exception from HRESULT: 0x80131515)	C:\Users\Admin\Downloads\WatermarkTextBoxExample\WatermarkTextBoxExample\WatermarkTextBoxExample\MainPage.xaml	1	1	WatermarkTextBoxExample

Please help me to execute the project. I am trying to learn windows phone 7 application development.

Thanks in advance.