Audio Output from Mac Pro not working in XP

In Vista, there is Sound control panel, and you need to have something plugged into the rear audio port. I have mine going to set of external speakers and booster.

I have the same problem that's been going around the web with my new unibody mac making cracking noises from the speaker in Vista/XP. I'm running Vista 32 and have installed this software called vista auto-lag and it seems to have alleviated some of it. It apparently has something to do with the drivers related the audio and the wireless networking.

Most issues in windows are around drivers - more so on laptops than on desktops for sure.

I think I resolved this! I had the same issues you have been having for a few months. I am actually running Vista. Here is what I did...

1. While booted to Windows I uninstalled boot camp
2. Re-installed boot camp from Leopard DVD
3. Installed boot camp update 2.1 (downloaded from Apple support, i know this is for XP only, but I updated anyway.)
4. Downloaded the realtek drivers (high definition audio codecs) from http://www.realtek.com.tw/downloads/
5. DO NOT use the Realtek installer to install the drivers...instead extract the contents to a folder.
6. Go to the device manager, locate the High Definition Audio device and updated the drivers from here (point to the folder where you extracted the drivers).

I now have sound out of the rear jack!! Hope this help someone

Regards,
Blaine

One caveat...The RealTek Sound Manager will try to install itself when you reboot. If this happens sound won't work anymore. You have to uninstall the RealTek Sound Manager via "uninstall" under the control panel. Reboot...re-apply drivers, then go into MSconfig (Startup Tab) and disable the start up of two RealTek processes (HD Audio Control Panel & RealTek Voice Manager).

Also, I noticed the when booting from OS X back to Windows, I had to unplug/plug the mini jack for sound to work. This seems to be a random occurrence.