I do this once a quarter on my Alienware X51-R1 to stay current.
Intel Chipset update Run this easy to use Intel Driver Update Utility and it will automatically tell you if you need to update your chipset INF file, and if so, will prompt you to install. Once installed, Click Start- Intel Driver Update Utility- Intel Driver Update Utility 2.0. Then click "Auto detect...".
Once you have done the above Intel Chipset update and restarted the computer, proceed to the Realtek installation below.
Realtek HD Audio update I have the Dell Alienware X51-R1 with the onboard Realtek audio. * Go here * Click "High Definition Audio Codecs (Software)" * Accept the notice * Click Next * Look to the right of "64bits Vista, Windows7, Windows8, Windows8.1 Driver only (Executable file)" * Click the Global link * The file will want to download. Tell it where to save the file so you can find it * Run the file. Follow the instructions and restart the system when done. Re-test the audio when done
Simple Realtek HD Audio check * Restart the computer * Press F2 * Open Advanced * Open Onboard Device Confugration * Open Onboard Audio Controller * Set to Enabled * Press F10 to Save and Exit * Once back into Windows, open the Device Manager * Click the + by Sound, video and game controllers * It should state Realtek Audio Codec controller. If it does, then the driver is installed correctly * Close the Device Manager * Right-click the Speaker icon on the taskbar * Left-click Playback Devices * Right-click Realtek audio * Left-click Set as Default Device * Re-test the rear green audio out jack using standard headphones