I had this same problem with my IDT High definition CODEC,
I followed your steps downloading and installing both files and rebooting etc.
Now in device manager the SigmaTel HD Audio Codec has installed but it says
'This device is not working properly because windows cannot load the drivers required for this device (Code 31)'
This laptop isnt a dell but i assumed this process would work the same way, its a packard bell, unfortuntly their website for some reason dosnt have this specific laptop in their support list. Easynote skype edition GN45. Im a little lost as i got this from a friend, i dont really know whats previously been done to it or changed but theyre not techy people so wouldnt have messed with the hardware and im trying to fix it.
Any help would be great.