No sound :(

[legoman]

Hi all
I have a realy silly problem. I can't hear anything in this game! No gunshots,no music...nothing! I already tried to run it in compatible XP mode (service pack 3), but that also did nothing. Please help meee!
my hardware is:
CPU: E6550 (2x 2,33 Ghz)
GPU: 8800 GTS (640 Vram)
RAM: 2 Gb DDR2
HDD: Seagate Baracuda 320 Gb

RUNNING ON Windows 7 (64 bit)

I suppose it's the operation system isn't it?