In Visual Studio 2005 the XSD compiler was in the SDK/v2.0 directory. In Visual Studio there is only a SDK/v3.5 directory has gone and so too has the xsd.exe compiler. Where
Windows 10:
C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6 Tools
Or on a 64 bit machine:
C:\Program Files (x86)\Microsoft SDKs\Windows\v10.0A\bin\NETFX 4.6 Tools\x64