olnorton: Depending on your motherboard, you will have something like Realtek HD Audio Manager.
The pic is what the Realtek one looks like.
Just set it to headphones.
I know Witcher 2 used to have problems with 5:1 surround sound.
Hmm I can't seem to enable or disable surround speakers and I'm not sure how to get that pop-up. I may have an outdated version of the audio manager, I'll see if I can find a new version.
EDIT: I don't think it's outdated, the site says the latest version was released in 2017 and I built this PC just a couple months ago (after which I made sure to run Windows Update until I couldn't run it anymore).