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Just use the official drivers from Apple, don't use other drivers off the Internet.
Download the latest Bootcamp drivers from Apple.com.

Wow. I've even registered into MacRumors just to say that this guy had the simplest and most correct answer! Theres a patch on Apple.com for bootcamp that solves some of these problems (specially mine, which was: sound coming out from the speakers, but not from headphones).

http://support.apple.com/downloads/#macoscomponents
Worth a click :)
 
Eureka!

I have experienced quite an odd problem with sound when running windows on my macbook in bootcamp. If i turn off or restart the laptop when the volume is muted, the next time i start it there will be no sound of any kind working. When i try to turn up the volume nothing happens (the usual mac volume turn up/down noise dosnt even happen). The only way to get any sound again is to make sure the volume is up and then restart the laptop. This is a really annoying thing, and i'm guessing its a problem with boot camp. Has anyone else experienced this?

Thank you! Thank you! Thank you! I've been having this problem for over a year and as soon as I read your post I realized that THAT is exactly what was happening to me! I couldn't figure out why I would sometimes have sound but mostly not. I would often mute my computer so it wouldn't make noise while my wife was watching t.v. I did notice lately that after it booted up the 'red circle with slash' over the speaker would be there but even after raising the volume or taking 'Mute' off, there would still be no sound. Now I get it. I need to raise the volume on my mac before I shut down. Thanks again!!!!!
 
No sound in BootCamp

This is an old thread but just in case someone still has the problem as I did when I just reinstalled bootcamp, try this:
After updating everything go to: control panel
sounds and audio
audio tab
sound playback box
change the default device.
Mine defaults to ATI, but my driver is the Cirrus. Choosing this in the speaker properties tab does not work.
 
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