did you try checking in device manager that whether your device drivers have been crapped. try re-installing the drivers for your sound card.
i feel that your directx install has some problems. you will have to re-install directx. you can always try "system file-checker" to go back to 8.1 but be aware that this will end you up with no updates installed. you will have to install all the updates once again.
did you make a restore point. did you try going back to a restore point?