Does the Sony site list an earlier version sound driver
When you uninstall/reinstall you need to uninstall, restart the PC and then reinstall. If you just uninstall/reinstall without restarting the original problem can still be there.
One more thing to try, go to the Device Manager, RIGHT click on the entry for the device and then LEFT click "Uninstall". Also check the box to uninstall the drivers
then restart the PC and Windows will detect and reinstall the sound (and may use a Sony driver or it may use some other driver). If the sound works, you are back in business.