If you lost the sound on your computer suddenly and if you have problem in installing the driver for the sound card then possibly the problem could be with the Windows Audio End Point Builder Service.
This service might stopped or corrupted. You can try starting the service, if the problem persist then you have to look at the registry settings.
Click Start -> Run
Type regedit and click Ok
Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Audiosrv\DependOnService and remove all the offending values except RPCSS
Close the registry editor and reboot the computer.
Now reinstalled the driver for the sound card and make sure the Windows Audio End Point Builder Service is started.