|You don't need to install SP1 or 2 in order to install SP3. |
Why do you say the drivers are not working? Go to device manager and look at the sound listing for Realtek. If Windows says the device is working properly then the drivers are OK.
If that is the case you may just need to confugure the ports. Do you have the Realtek sound manager icon in the tray by the clock? If so, open it and use to map the ports according to how you have the wiring connected. Also check to verify nothing is muted. Re-installing sound results in the device being muted many times.