Right,
I've been trying to fix this issue for the last 4 months also.
I've had a breakthrough this evening combing through the drivers.
Hit Windows + R / right click windows --> run
type devmgmt.msc
Find the drop down for "system devices"
Find the one called Intel(R) Smart Sound Technology (Intel(R) SST) OED - it'll probably have an icon on the left with a yellow triangle.
Right Click - update driver.
Fixed the sound issue for me.