Sound outputs either from the onboard sound chip on the motherboard, or through an add-in soundcard. Download whatever drivers are needed for the onboard sound to function, and then check the sounds portion of the control panel to make sure an output device is listed. After that, it should just be a matter of selecting your speakers.
A USB based headset usually has its own onboard sound chip, so all that would be needed is to select it from the sounds tab of the control panel.
You mean he should download drivers for the headset? Because at the moment he doesn't have any speakers... And for the motherboard we already tried to update it with the disc and I googled the motherboard but no real results...