No sound on windows bootcamp; Mac 13"

Topic.

On my new 15" macbook pro the sound and video works fine. On my sisters 13" that is about a year old, I tried to install Age of Empires III and found that there were no video card drivers. I managed to install the Nvidia driver, and it worked. However, there is (and has never been) any sound on the windows half.

dxdiag has sound 1 and sound 2: where it says the driver is HdAudio.sys, however I could not find a driver for this. I installed the realtek drivers, and this also didn't work. (P.S, I have restarted multiple times.)

Is there a simple answer?

 

I fixed the problem by installing the mac osx install dvd of my 15" rather than the 13". now it works fine.