I have spent the last day looking at fixes for DX10, sweetfx and Windows 8.1. I understand they do not support it but I found a 'fix' using RadeonPro. But my core of my problems lies with the SweetFX DXGI dll. It prevents my FSX from opening when using it with DX10. Without the DXGI DLL my sweetFX does not work in FSX. Is there any fix? 

Is there really no solution? I've the same problem :(

There is a suggestion in the " dx10 how to guide" on nzfsim to reinstall directx, download the guide and have a read, I cannot verify this, I have never encountered a problem with sweetfx in the past.