Once you are in the BIOS, it will have several menus (i.e. Main, Advanced, Power, Security, Boot, and Exit).  The one you want is the Advanced Menu.  Under the Advanced menu, select the option (it is probably the last one in the list) for Onboard Device Settings.  This is almost certainly where the option to turn off motherboard features like the integrated sound and/or video will be located.
FYI, the person helping you can download the user manual for your system at the following web link:
http://www.trigem.com/support/manuals.asp
I'd access it using Internet Explorer, though, as the website seems to have issues with other web browsers (it throws errors with Firefox and Chrome about content being corrupted on downloads).