Hi,
If you experience issues in which an application fails because of the missing file X3DAUDIO1_7.DLL, you may be able to resolve the failure by running the DirectX run-time package.
I would suggest you to download the the Runtime Package and then installing it.
http://www.microsoft.com/en-us/download/confirmation.aspx?id=8109
Also, you can diagnose basic problems with DirectX
http://windows.microsoft.com/en-ca/windows-8/diagnosing-problems-directx
Let us know if it helps. If the issue persists, we would be happy to help you further.