Can't Get Any 5.1 Sound To Work

I bought a computer second hand, and all in all it's an upgrade from my last computer, except for one thing: I can not for the world get my speakers to play any kind of 5.1 sound.

The sound drivers installed are Realtek High Definition Audio 6.0.1.6602 - but this could be a mistake on my side, as for all I know, I'm not even supposed to have them installed. I just assumed I needed the Realtek Audio Manager like I did on my last computer, to get the 5.1 sound to work, and this is probably completely wrong, heh.

So how can I get the 5.1 sound to work? What information do you need to guide me? And how do I find that information?

If the motherboard type is needed (I read somewhere else it might be) then I assume it's this: ASUSTeK Computer INC. 2A73h 1.01

When I go to the Control Panel, there is no Realtek Audio Manager there. Clicking Sound, I get the following information:

Speakers
Realtek High Definition Audio
Default Device

Clicking Configure, I only have ONE option: Stereo. No 5.1.

I really want the option to listen to sound from all my speakers (I don't even care if it's pure 5.1 sound, as long as there's music/sound coming from all the speakers I'm happy!)