Is there an icon of a speaker on the taskbar (that bar thingy on the bottom(?) of the screen), maybe it may only become visible when you click that left arrow, if there is, righclick that and open the sound device and see if the sound level(s) are halfway and there is no warning sign with a cross - this means the sound is off and you have to click that to turn it on.
If all is ok there, make sure that the speakers are connected properly to the computer and they get power.