Counter Strike 1.6 on Windows XP guest of Virtual Box on Mac Mouse Issue

counter-strikemouse

My brother installed Counter Strike 1.6 on his Macbook Pro using VirtualBox and Windows XP as guest OS. The game installed and running fine but he has issue with mouse. As you may know Moutain Lion has mouse acceleration of the sort so it's being implied in the game. The mouse works but in circular direction and need very accurate movement to move.