I wouldn't advise downloading a 3rd party driver you find on various websites because you'll end up reinstalling Windows. Realtek is very problematic when it comes to drivers and laptops, therefore the only way to download the audio driver in order to have 5.1 Audio support is only through the official website of the laptop's manufacturer. This means you should use Google and type the model of your laptop along with its brand. Locate the Support section on the manufacturer's website and then download the official driver.
I speak from personal experience, install only the driver from the manufacturer's website.