Visual Studio 2010 incorrectly using Windows SDK v8.0A path
===

I've recently uninstalled the Visual Studio 2013 (I think) developer preview and now Visual Studio 2010 has started giving me the following error:

> Error	1	Task could not find "sgen.exe" using the SdkToolsPath "" or
> the registry key "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft
> SDKs\Windows\v8.0A". Make sure the SdkToolsPath is set and the tool
> exists in the correct processor specific location under the
> SdkToolsPath and that the Microsoft Windows SDK is
> installed	C:\tfs_views\Platform\Main\AMC2000\DotNet\Configuration\ConfigModel\ConfigModel\ConfigModel\ConfigModel.csproj	111	5	ConfigModel
> (ConfigModel\ConfigModel)

Due to a custom build step (described [here](http://stackoverflow.com/questions/134224/generating-an-xml-serialization-assembly-as-part-of-my-build))

I have found [this question](http://stackoverflow.com/questions/2731365/running-msbuild-fails-to-read-sdktoolspath) which described a similar error.  In this case the resolution is to install the Windows SDK v7.1 on the build machine, however I already have the correct version of the SDK (v7.1) installed, Visual Studio is choosing to use the incorrect version (v8.0A).

How can I fix Visual Studio to use the correct SDK again?