You don't even have to disable it, just don't use it. Use your sound card -- well, if you had one. According to your pictures, you don't have any, as there's no other audio device either in this section, not in the currently non-existant other/unknown devices section.
If your motherboard has integrated audio, your first task is enabling it in the BIOS, because accourding to your pictures, it's disabled.
If your motherboard has no audio support, it's time to get a PCI sound card.
CPU: AMD Phenom II X4 810 @ 3120MHz | RAM: Kingmax 2x2GB DDR2 800 @ 833MHz| MoBo: MSI K9A2 CF v1.0 (BIOS: 1.D)| GPU: Asus HD 6850 1024MB (DirectCu) @ 835/1135MHz | Display: L24FHD | PSU: PC Power & Cooling Silencer 750 Quad | OS: MS Windows 3.11 Pro x64