Where can i download a free copy of multimedia audio controller for microsoft windows xp home edition?

Trying to fix the audio on my computer has been really frustrating for my husband and I because I'm not very good with computers and neither is he. I do not have the disc that came with this computer, so i cannot reinstall the mutlimedia audio controller that way. Where can I download it for free? I have a microsoft windows xp home edition Version 5.1.2600 Service Pack 2 Build 2600. the system manufacturer is SYS. The system model is snc302eeh. I need to know exactly which multimedia audio controller to install and the exact site that I can find it on. Any help will be greatly appreciated. Thanks in advance!