ale jaki plik SDK???
Przecież MS wyraźnie pisze
Visual Studio 2010 does not support mobile application development for versions of Windows Phone prior to Windows Phone OS 7.0.
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Because Visual Studio 2010 does not support mobile application development for Windows Phone prior to Windows Phone OS 7.0, you cannot use the following features: .NET Compact Framework projects, Visual C++ device projects, smart device CAB projects, Device Emulator and Device Emulator Manager, testing tools for device projects, and Device Security Manager.
Mobile application development is still supported in earlier versions of Visual Studio, such as Visual Studio 2008. For more information about smart device projects, see Windows Mobile Developer Center and Smart Device Development in Visual Studio 2008.
czyli jeszcze raz MS VS 2010 NIE WSPIERA net cf. Koniec, kropka. Chcesz móc pisać na cf kup 2008 (jak masz 2010 to chyba możliwe jest pobranie wersji 2008)