Internal Speakers not working in Vista Ultimate (using Macbook Pro)

Hi, I just put Windows Vista Ultimate via Boot Camp on my Macbook Pro.
The speakers aren't working and I'm not sure whats wrong, if i press the speaker volume keys on the keyboard it looks like its working on the screen but i still don't hear anything. I also checked my Realtek Audio Manager and it says that its working I just cant hear anything.
Any help is appreciated, thanks.