In most cases, if you have installed DirectX 11, you can play most games after you have diskless boot Windows 7 with CCBoot. DirectX 11 can do what both DirectX 10 and DirectX 9 do. But sometimes, few games can not run with DirectX 11, they need DirectX 9. Fortunately, we can install multiple DirectX on Windows 7 and directx 9 for windows 7.
When trying to install another DirectX on Windows 7, you may get an error like - a cabinet file necessary for installation cannot be trusted. Please verify the Cryptographic Services are enabled and the cabinet file is valid. To fix this issue, please download dxwebsetup.exe from http://www.microsoft.com/download/en/details.aspx?id=35 and install it.
If the error persists, please refer to this discussion and slimdx.org for more helpful information.