src:
http://msdn.microsoft.com/en-us/windows/hardware/hh852365.aspx

notes:
14'3/18 : WDK is embedded in Vistual Studio package

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WDK and WinDbg downloads

This is the place to get your Windows Driver Kit (WDK, formerly DDK) and WinDbg downloads, including the Windows 7 release of the Debugging Tools for Windows, which works for Windows XP. The debugging tools are included in the WDK, but you can also download them separately here.

The WDK has the tools you need to develop drivers. WDK 8.1 is integrated into Visual Studio Professional 2013 and Visual Studio Ultimate 2013 and gives you most of the tools you need for developing, building, packaging, testing, and debugging drivers.

Not sure which kit to use? The tables in Windows Driver Development can help you make the right choice.