Check the audio settings in control panel for a start, see what audio devices are set for what, try changing them around. Might help with a bit more info, onboard audio or sound card ?
Not knowing which, I'd say go into the BIOS and check the settings for that.
If you have a sound card, disable onboard... otherwise make sure onboard is on.
Possibly the speaker inside may be attached to an audio header... does your computer have 3.5mm sockets on the back/front ?
Hard to say without more info.