maybe your speakers are turned off.. check the control panel if its in mute... for some reason, my pc mutes when i press the CTRL key...
or in your presentation settings ( in the game itself) , check to see if the sounds are off...
i don't know if it has any relation to you problem but you can check your directx settings and check the sound tab... to go there, run "dxdiag" without quotations on start --> run...
if it is a burned copy of the game, well.. you got burned...
hope it helps..
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