I've read that many people have been struggling to get the rear audio jack their Mac Pro to behave under bootcamp. The issue stems from the Realtek drivers 'Jack Detection' which normally allows windows to detect when you plug in headphones or speakers. On some Windows PC's the Realtek Audio Manager has the option to disable this detection, but the latest drivers don't include any advanced options. Anyway, I've found a decent solution: Fix Using the registry editor, find all instances of ForceDisableJD and change the value from 00 to FF. This will force audio to be output from the rear jack (and front jack) at all times.