Right click on the volume Icon in the system notification area, [Lower right taskbar]. choose adjust audio properties. remove tick from mute if there.
Click on the first Advanced button and again check there are no ticks in any box's. Now click on options, [top left of same window] then on properties and place a tick in all the box's that apply.
Right click on the volume Icon again, choose adjust audio properties and this time click on the second "Lower" advanced button and check that the correct configuration for your speakers is displayed. IE: 2.1 or 5.1
If you have already tried all these and they are set as should be. Try re-installing the sound drivers from the Motherboard CD. Also check all leads are fully pushed home and the "Volume button on the speakers themselves is turn on/up.
If you can confirm all this as been checked and re-checked then please post back for someone to help further. j.