We’ve identified an issue for users of the Microsoft Windows SDK for Windows 7 and .NET Framework 4 (Windows SDK v7.1). If you have downloaded and installed the stand-alone Windows SDK v7.1 and you are using the x64 or IA64 compilers that were included in that download, you may find that these compilers and the associated Visual C++ library files removed. The impact may be as indicated below:
Please see this article for more information about the issue, and how to restore the SDK compilers to a working state.
We recommend that users of the Windows SDK do not install Visual Studio 2010 Service Pack 1 at this time, since there is no workaround for this issue. We are currently working on an update to fix this issue and will post more information when it becomes available.