With the 6GB installed, go to the Device Manager and see what it shows for status, either an error and code or working properly. The code can help in troubleshooting.
But, in either case, RIGHT click on the entry for the sound and then LEFT click "uninstall". DO NOT click the box to uninstall the drivers
. Then restart the PC and note if Windows detects and reinstalls the sound. If it reinstalls, check the status .